The Late Paleozoic strata are well exposed in Yongchang County, Gansu Province, Northwest China. The strata contain numerous plant fossils. Hence, Yongchang County is a good location to study Paleozoic plants and plate movement. Using well-preserved cordaitean cones and seeds from the lower Permian Taiyuan Formation of Yongchang County, two new species of fossil plants are described, one attributed to the new organ genus Hexianthus (H. shenii sp. nov.) and the other to the seed genus Samaropsis (S. shenii sp. nov.). The micro- and macro-scale features of the cones, including the epidermal features of the bracts and scales, are analyzed in the laboratory. Numerous cordaitean cones with helically arranged bracts and scales (H. shenii sp. nov.) present in the Taiyuan Formation of Yongchang County share similar characteristics with the cordaitean cones which are endemic to the Cathaysian flora. This suggests that the study region was characterized by the Cathaysian flora in the Cisuralian, similar to the Hexi Corridor to the south of the study region. Based on the study of fossil cuticles and their associated plants, the study region of Yongchang County probably had a warm and humid climate during the Cisuralian. In addition, according to the associations between different fossil plants from several localities in Gansu Province (from the Cathaysian flora in the lower Permian to the Cathaysian-Angaran mixed flora in the upper Permian), a possible boundary between the Cathaysian and Angaran floras in Gansu Province can be placed along the Hexi Corridor, which provides important information for the study of floral associations in Northwest China during the Late Paleozoic.