Abstract: What analyzed in the present paper is the distribution, diversification, origin and relationship os 20 primitive angiosperm families occurring commonly on both sides of the Taiwan Strait, China. The results confirm the floristic integrity on both sides and reveal that the Taiwan flora have mixed elements from the eastern Asiatic flora and the Malesian flora, but mainly belonging to the former. The abundant endemic species in the primitive families of the Taiwan flora are mostly neoendemic elements, which formed after the separation of Taiwan from the mainland. The primitive angiosperm genera and families in Taiwan and Mainland China have a common origin and the origin time and place could be dated back to the Late Cretaceous in the Cathaysian ancient land before Taiwan firstly seperated from the mainland in the Mesozoic. The land bridge during the Quaternary glacier between Taiwan and Mainland China had seldomly affected the distribution of primitive angiosperms on both sides of the Taiwan Strait.

Key words: Both sides of the Taiwan Strait