Abstract: Tetraena Maxim. is an endemic genus of Inner Mongolia and the desert region of Central Asia. It is also a rare and endangered plant. Some botanists had made some research on the systematic positions of this genus, but their views are debatable. Through a comprehensive study: research history, morphology (pistil, fruit), pollen grains, chromosomes, the authors sug- gest that this genus be separated from Zygophylloideae (Zygophyllaceae, Takhtajan. 1987) and a new subfamily-Tetraenoideae be set up for it. A key to subfamilies of Zygophyllaceae (sen. str.) is provided. The systematic position of Tetraena Maxim. is: Rutales-Zygophyllaceae -Tetraenoideae-Tetraena.