Abstract: 【Objective】Seedling regeneration is an important part of natural succession and vegetation restoration, and studying the relationship between seedling regeneration and environmental factors could provide useful information for managing natural secondary forests.【Method】We selected four sampling plots that were typical subtropical secondary forest communities in the Lishui Forestry Farm, Jiangsu Province, China, studied the size-density distribution characteristics of Ilex chinensis seedlings in each plot. On this basis, we analyzed the relationships between I.chinensis seedlings and three kinds of environmental factors, including intraspecific, interspecific, and soil factors, by the method of the redundancy analysis(RDA).【Result】With increasing importance value of I.chinensis in different communities, size-density distribution characteristic become from ‘high density-small size' to ‘low density-big size'. In general, three kinds of environmental factors promoted seedling regeneration, but there were differences between the factors. In communities with high I. chinensis importance values, the stand structure factors, including intraspecific and interspecific factors, were dominant, and the interspecific interactions mainly shows in main story. With decreasing I. chinensis importance values, the influence of soil factors gradually exceeded that of the stand structure factors, and interspecific interactions in the regeneration layer became stronger.【Conclusion】In the mountainous region of southern Jiangsu Province, dominant factors affecting seedling regeneration vary by community type, and the effects of environmental factors change with importance value of I.chinensis.