Abstract: According to chemical constituents, plant morphology and geographic distribution of Thalictrum in China, the relationships among sections in the genus are discussed in the present paper. The results show: 1. China is one of the major distribution centers of Thalictrum plants, with half of species endemic. Compared with species in other regions of the world, Chinese ones are relatively primitive. 2. From the chemosystematic point of view, the system of the genus adopted in Fl. Reip. Pop. Sin. is reasonable. 3. The main constituents of Thalictrum plants are benzylisoquinoline alkaloids. A correlation exists between the chemical patterns and plant evolution. The different sections are of different structure types. Aporphine-benzylisoquinoline and bisbenzylisoquinoline are major constituents in Sect. Leptostigma. Sect. Tripterium contains mainly aporphines, but non-alkaloid compounds are principal constituents in several species. In Sects. Thalictum and Schlagintweitella and Subgen. Leconyerium, types and content of alkaloids increase obviously and thus there are medicinal species. So these sections should be interested in developing some active constituents of antitumor, hypotenstion and antibacterium. 4. The genus occupies a special position in Ranunculaceae, as a transition to link the follicle plants and achene plants. Meanwhile, because the genus is rich in benzylisoquinoline alkaloids, the opinion that the Ranunculaceae, Berberidaceae, Menispermaceae andPapaveraceae form a natural group is even more strongly supported.

Key words: Thalictrum, Chemosystematics, benzylisoquinoline alkaloids