Abstract: The species diversity of 20 broad-leaved deciduous forest communities in the mid- and southwestern parts of the warm-temperate zone were analyzed and compared. The results were as follows: 1) in general, species abundance (Sp) and diversity (D and H′) of herb layers were the highest in most of the 20 forest communities, followed by the shrub and tree layers sequentially; in contrast, the index of Alatalo evenness(Ea) was usually the highest in the shrub layer; 2) communities at the sub-climax stage also showed different trends in diversity among layers--diversity indices (D and H′) were lowest in the tree layers followed the herb and shrub layers sequentially; 3) eveness in different layers were all >0.5 in climax and sub-climax stage communities; 4) using total community importance value (IV) as a measure of the total indices of those communities, it was found that Simpson’s index (D) can be used to describe community stability. That is, early succession stage communities and those distributed in particular habitats have total D lower than or close to 0. 5. On the other hand, in zonal communities--typically highly stable or at a climax stage—have both D>0.5 and total Ea>total D. Communities with total Ea less than or close to their total D have higher species abundance, and are comparatively stable or at the stage just before climax, i.e. sub-climax stage in the sere.