Abstract: On the basis of distribution information at large-scale,the latitudinal patterns of genus diversity of seed plants in Yunnan with a regard to their floristic origins were examined. The results showed that tropical genus diversity was negatively correlated with latitudinal gradient, suggesting a south-to-north spreading trend; however, temperate genus diversity showed positive correlation with latitudinal gradient, implying a north-to-south spreading trend. The total genus diversity and diversity of tropical genera shared the similar decreasing latitudinal patterns. It is suggested that Rapoport’s rule may be more applicable to explain the latitudinal patterns of species diversity originated from tropical regions. It is also suggested that the hypothesis of floristic origins is probably one of the effective theories to explain latitudinal patterns of taxa diversity