Abstract: The poplars (Salicaceae Mirbel subfam.Populoideae Kimura) contain two genera (i.e.Balsamiflua et Populus) with more than 50 natural species (as well as a great number of natural hybrids et artificial hybrids),and distribute naturally in Tropical Africa et in the Northern Hemisphere roughly from 19° to 70° north latitude;Balsamiflua of about 8 species disperses disjunctively in Equatorial Africa,Tethys regions et southeastern North America;Populus of more than 40 species widely ranges in Africa,Asia,Europe et North America approximately between the Tropic of Cancer and the Arctic Circle.It is probable that the salicaceous late ancestor originated from the West Gondwana land during the Early Cretaceous,and gradually developed into extant poplars (i.e. Balsamiflua et Populus) et extant willows (i.e.Pleiarina,Chosenia et Salix) through two intermediate links (i.e.Archaic poplar group et Archaic willow group) respectively.The Archaic poplar group (i.e. the direct ancestor of the poplars) probably emerged from the West Gondwana land during the Middle Cretaceous;subsequently,it seattered over the areas concerned (especially the north Laurasia),and differentiated et evolved further in the course of its migrating.The genus Balsamiflua possibly occurred in Africa land during the Middle et Late Cretaceous,and dispersed progressively into the Laurasia;then,the unitary Balsamiflua flora was divided into several distant parts developing alone owing to the breakup of the Laurasia et the formation of the Sahara.The genus Populus might rose and differentiated in eastern Tethys regions during the Middle et Late Tertiary;afterwardz,it widely spread in Eurasia land and gradually migrated to North America land via Bering regions.Besides,a conspectus of all the genera and species of the plants concerned and a key to the subfamilies et genera of Willow Family are provided in the present paper.