Based on the diversity data of seed plants in six floras of the Tibetan Plateau (TP), we conducted a comprehensive analysis of families and genera diversity, the similarity of species composition, and the spatial distribution patterns of diversity. We quantified the influences of climate, topography, and historical factors on the distribution patterns of seed plant species diversity, and investigated the underlying reasons for the formation of different diversity patterns of different seed plant flora in the TP. The results indicate that, herbs were the main seed plant species in all six floristic regions of the TP (averaging 68.69%), among which the IIIE14 region (Hengduan Mountains region) has the richest diversity of seed plant species (8,786 species), while the IIIF18 region (Western Himalaya region) has the least seed plant species (1,341 species). Asteraceae (12.34%) and Rhododendron (3.19%) are the dominant family and genera in the flora of the TP, respectively. At both the plant families and genera levels, the similarity coefficients is the highest between the IIIE14 region and the IIIE15 region (Eastern Himalaya region) (0.8500 and 0.7225, respectively), and the similarity coefficient is the lowest between the IIIE15 region and the IIC6 region (Kashgar region) (0.4444 and 0.2594, respectively). At the species level, the similarity coefficient is the highest between the IIIF16 region (Tanggula region) and the IIC6 region (0.4673), and the similarity coefficient is the lowest between the IIIE14 region and the IIIF18 region (0.0822). The overall pattern of floristic diversity in the TP shows a general trend of more diversity in the southeast and less in the northwest. Climate, topography and historical factors jointly determine the floristic diversity of the TP. Among them, Elevation Range has an important impact on the IIIE14 region (mean 15.49%), the IIIF17 region (mean 25.46%), the IIIF18 region (mean 30.96%), Topographic Heterogeneity on the IIIE15 region (mean 18.14%), Annual Mean Temperature on the IIIF16 region (mean 18.04%), and Annual Precipitation and Actual Evapotranspiration on the construction of seed plant Species Richness and Phylogenetic Diversity in the IIC6 region (mean 22.94% and 24.95%, respectively). The above results indicate that the different environmental characteristics, geological history, and climate change history within the plateau have contributed to the diversification of the floras of the TP, forming a unique diversity pattern with significant differences but certain similarities in the TP today. This study provides a scientific basis for revealing the formation and evolution of biodiversity in different regions of the TP.