Grey correlation analysis was used to study the efects of vegetation status on species diversty of tree seedlings in a subtropical evergreen forest in Dujiangyan (Sichuan Province)．Twenty-two plots with 5 m×5 m each in a sample site of 10 m×55 m were investigated． Data obtained included plant species，number of individuals，plant height，diameter at breast height，and canopy coverage in tree layer；plant species density and coverage in shrub and herb layers；and species, individuals and plant age of tree seedlings above 13 m．Species abundance index (S)，Simpson index (D)，Shannon-Wiener index (H), and Pielou evenness index (E) were used in α-diversity analysis. The results indicate that the parameters of vegetation status affecting species diversib, of tree seedlings are greater in D in herb layer, and H and coverage in shrub layers；but less in H in shrub layer an dcoverage in herb layer．The effect of vegetation status on the four species-diversty indexes are in the order Pielou evenness index>Shannon-Wiener index>species abundance index>Simpson index．