Abstract: In recent years , taxonomic correlation between species richness of different taxonomic groups has been an active issue in biodiversity studies. However , there are cont radictory results. We collected species checklists from three geographic regions : zoogeographic regions , administ rative regions and nature reserves in China. We analyzed both correlation and ratio of avian and mammalian species richness in these regions. We also calculated the correlation and species ratios of bird and mammals in different latitudinal and longitudinal regions. Our result s showed that there were significant correlations ( p < 0.01) between the bird and mammal species richness in each of those regions. All avian and mammalian species richness correlation coefficients were higher than 0. 85 except that of nature reserves , 0. 818 , and that of the North China Region , 0. 768. Therefore , the high correlation between avian and mammalian species richness may have predictive values. There were no significant differences ( p > 0.20) among species ratios of birds and mammals except those of different zoogeographic regions ( p < 0.05) . The bird and mammal species ratio in China was lower in the central region but higher in the border regions with the highest value from northeast China. We also studied the difference in species richness and species ratios calculated with historically accumulated species checklists and modern species checklist . The correlation coefficient calculated with accumulated species checklists was less than that calculated with the modern species checklist , but the bird and mammal species ratio was higher than that calculated with modern data. Finally , we explored why the bird and mammal species richness are correlated. According to the species-area formula , S = CA^Z ,we deduced the correlation relationship of these taxonomic groups. When we analyzed all species richness data of bird and mammals , we found Z₁/ Z₂ = 0. 913 , thus , C₁/ C₂ approximates R_am . The study can be extended to other taxa. The species richness correlation provides us a means for rapid assessment of species diversity.