The paleoflora of the Yaojie Formation in Gansu Province and its paleogeographcial features were studied in this paper. A total of 31 genera including 63 species were identified, including newly discovered Gonatosorus shansiensis. Ginkgopsida (36.5%) and Filicopsida (22.2%) are most abundant, and Coniferopsida (17.5%) and Cycadopsida (15.9%) are less abundant, followed by Sphenoposida (6%) and Fructus et Semina (1.9%). On the basis of fossil compositions and time characteristics indicated by the flora, comparison with some similar floras at home and abroad, suggest that the geological age of the Yaojie Formation should belong to the Aalenian to Bajocian period. The cluster analysis was employed to compare the Yaojie flora of Gansu with other 11 flora from northern China to discuss the geographic attribution of the Yaojie flora, and the Middle Jurassic flora in northern China was preliminarily classified. In addition, the branch biogeographic method was used to analyze the affinity relation of the Yaojie flora. The results show that the Middle Jurassic Yaojie flora has close affinity to the Gaotouyao flora in Inner Mongolia. This study also investigated the geographical distribution characteristic of the genus Gonatosorus in the Mesozoic of China, which was newly discovered Yaojie of Gansu. It is basically in agreement to the division of the Middle Jurassic in northern China. The results show that Yaojie flora belongs to the Siberian flora region and has a close relationship with Gaotouyao flora in Inner Mongolia, the two floras can be classified as a small plant subordinate in Siberian flora region, and the boundary between the Siberian and EuropeChina flora region is supposed in the south of Yaojie flora.