Abstract: The surface ultrastructure of seeds of chinese Cuscuta was observed under SEM. The main results are as follows: the seed surface could be divided into three parts: hilum, hilum-rim and spermoderm. The hilum is collar-shaped or higher or lower than level of hilum-tim. Hilum-rim cells are mostly radiately ar- ranged and less frequently in reticulate or other types of arrangement.  The spermoderm shows at least three patterns of ornamentation, cerebelloid, striate or irregular, on which some tuberculate or small clumps of granules could be found sometimes According to the surface ultrastructure of the hilum, hilum-rim and spermoderm, the observed dodder seeds could be divided into three types. The surface characters of dodder seeds are also important both for diagnosis ofspecies and for quarantine of dodders.