Abstract: The orchids represent one of the largest families of flowering plants in the world, Their flower structure is evolutionarily highly specialized and systematically, they are the most advanced groups in plant kingdom of the world. The babitat of orchids is more special than other families in flowering plants. Their distribution has higher regularity and possesses important significance for studying floristic character and region alization. The present paper proposes a concrete boundary between the Sino-Himalayan Subregion and the Sino-Japanese Subregion in Sichuan Province, based on the distribution patterns of some orchid genera typical of the two subregions. I. Risleya, Diplomeris, Diphylax and Platanthera subgen. Stigmatosa all belong to the typical groups of distribution in the Sino-Himalayan Subregion. Their distribution patterns are as follows: 1. Risleya (only one species) is distributed in Sikkim, N. Burma and S. W. China and grows at (1041--) 2900--4200 m alt. In China its distribution ranges from Xizang (Tibet) (Mainling and Bomi), Yunnan (Weixi) to Sichuan (Gongga Mountain and Emei Mountain (alt. 1041 m)). The Emei Mountain is its eastern limit (Fig. 1). 2. Diplomeris (only two species) is distributed in M. Nepal to Bhutan (alt. 500-1000 m), N. E. India, Burma, the northest Vietnam (Sa-Pa alt. 1000 m) and China and grows at (500---) 1500--2600 m alt. In China its distribution ranges from Xizang (Tibet) (Medog alt. 1000 m), Yunnan (Gongshan), Sichuan (Kangding, Hejiang and Xuyong), Guizhou (Xingyi) to Guangxi (Mashan). Hejiang in Sichuan is its eastern limit (Fig. 1) 3. Diphylax (only three species) is found in M. Nepal, Sikkim, N. Burma and S. W. China at (1750-) 2500--4200 m alt. In China its distribution ranges from Xizang (Yadong, Qonggyai, Medog and ZayÜ), Yunnan (Gongshan, Deqen and Yiliang alt. 1750 m), Sichuan (Emei Mountain alt. 1900 m) to Guizhou (Fanjing Mountain alt. 1800 m). The Emei Mountain is its eastern limit (Fig. 2). 4. Platanthera subgen. Stigmatosa (including 12 species) is found from Kashmir Re- gion, Pakistan (Hazara), through Nepal, Sikkim, Bhutan, N. India (Kumaon, Darjeeling, Simla), N. Burma to S. W. China at (1500-) 2300-4500 m alt. In China its distribution ranges from Xizang (Gyirong, Zhangmo, Rongxar, Dinggye, Yadong, Cora, Mainling, Bomi, Medog (alt. 1500 m), ZayÜ) through Yunnan (Gongshan, Deqen, Weixi, Fugong, Bijiang, Lijiang, Dali, Heqing, Luquan, Kunming and Jingdong), Sichuan (Muli, Miyi, Huili, Huidong, Puge, Xichang, Xide, Maianning, Yuexi, Meigu, Erlang Mountain, E- bian, Emei Mountain, Honya and Guan Xian) to Guizhou (Zhenfeng). The Emei Mountain is its eastern limit (Fig. 3-4). According to the structure of gynostemum and form of labellum of the subgenus. Stig- matosa, their species belong to Platanthera unquestionably, although they are different from the other members of Platanthera due to their inconvex stigma (not concave) and sepals with mammillary-ciliate. The stigma of this group exhibits a series of evolutionary trends: from stigma single, convexly elliptic and located near the rear of spur mouth (in P. stenantha) ; to stigma single, shape of a saddle, and located near the front of spur mouth (in P. bakeriana); and to stigma double, separately located at front of spur mouth (in other ten species). The Platanthera subgen. Stigmatosa is confined to the area from the south fringe of Xizang Plateau (from Kashmir Region to N. E. India) through N. Burma to the Hengdu- an Mountain Region in China. It seems that the subgenus. Stigmatosa has been affected by upheaval of this area, which caused a series of variation and differentiation uninterruptedly, giving rise to this group due to the long-term selection. The vertical distribution of Risleya, Diplomeris, Diphylax and Platanthera subgen. Stigmatiosa is higher in general, but little lower in some marginal regions of their distribu- tion. II. Neofinetia, Vexillabium and Sedirea all belong to typical groups of distribution in the Sino-Japanese Subregion. Their distribution patterns are as follows: 1. Neofinetia (only one species) is distributed in Japan: Honshu (west of Kanto), Shikoku, Kyushu (Tanega-shima, Yaku-shima), Ryukyu-qunto (Amamio-shima, Oki- Nawa-jima) and Daito-shoto; S. Korea (Cheju-do) and China and grows at 400--1300 (-- 1520) m alt. In China its distribution ranges from Fujian (Chongan), Zhejiang (Putuo, Shengsi and Songyang), Jiangxi Lushan Mountain, Yushan and Yichun, Hubei (Lichuan and Hefeng) to Sichuan (Wan Xian, Pingchang, Tongjiang, Guangyuan, Qingchuan (alt. 1520 m), Beichuan, Emei Mountain) and Gansu (Wen Xian). The Emei Mountain is its western limit (Fig. 5). 2. Vexillabium (only four species) is distributed in Japan: Honshu (Izu-hanto, Mieken), Shikoku (Yaku-shima); S. Korea (Cheju-do) ; N. Philippines (Batan Is. ) and China at 450-1300 (-1600) m alt. In China its distribution ranges from Taiwan (Taidong, Lan Yu), through Zhejiang (Lin’an, Tianmu Mountain and Suichuan), Hunan (Xinning), Shaanxi (Yang Xian) to Sichuan (Nan-chuan, Jinfo Mountain and Beichuan (alt. 1600 m)). The Minjiang River is its western limit (Fig. 6). 3. Sedirea (only two species) is distributed in Japan: Honshu, Shikoku, Kyushu (Tanega-shima, Yaku-shima and Nakano-shima) and Ryukyu-qunto (Amamio-shima and Okinawa-jima); S. Korea (Cheju-do) and China at 300--1300 (--1400) m alt. In China its distribution ranges from Fujian (Chong´an, Wuyi Mountain), Zhejiang (Wencheng, Tain- tai Mountain, Longquan, Lin'an, Xinchang and Kaihua), Hunan (Sangzhi, Shuangpai, Shaoyang and Tongdao), Hubei (Xianfeng), Sichuan (Chengkou and Leibo (alt. 1400 m)), Guizhou (Jiangkou and Songtao) and Yunnan (Yingjiang alt. 1350 m). The Leibo is its western limit (Fig. 7). The vertical distribution of Neofinetia, Vexillabium and Sedirea is lower in general, but little higher in western marginal regions of their distribution. Above distribution patterns can be summarized as follows: (1)Risleya, Diplomeris,Di- phylax and Platanthera subgen. Stigmatosa belong to typical groups of the Sino-Himalayan Subregion distribution,