Evolution of tropical forest and change of soil quality were studied quantitatively on Hainan Island based on investigation in field and analysis in lab. The results show that a type of varied secondary vegetation has been formed in tropical forestsdue to human disturbance different in extent. In the investigated region there are more than 36 types of vegetation communities, of which ten are of secondary dense forests, four secondary sparse forests,, eleven of shrubs, and eleven of meadows. The results also show that in terms of soil fertility, the four major types of vegetation are in a decreasing order of secondary forestlands > bushlands > meadows. The complicated relations between vegetation properties, vegetation and soil are mainly represented in: (1) close relationship between composition properties of the secondary vegetation and sharp variation of the relationship between nutrient elements in the soil; (2) correlation coefficients between properties of vegetation composition and concentration of various nutrient elements in the soil tend to be lower.