To reveal the effects of plant community functional trait changes, resulted from the land use conversion from primitive forest to secondary forest or plantations, on soil quality in tropical region, an investigation was conducted in five typical land use types in the central mountainous area of Hainan Island. The land use types include primitive forest (PF), secondary forest (SF), areca plantation (AP), pure rubber plantation(RP) and rubber intercropping Alpinia oxyphylla plantation (RAP).The changes of soil qualities after the natural forest conversion to secondary forest or plantations and the relationships between plant community functional traits (litter fall, canopy density, root length density, fine root density, and specific root length) and soil quality were analyzed. Compared with those of primitive forest, the litter fall, root length density, fine root density, total soil porosity, maximum water holding capacity, soil organic carbon, and total nitrogen of other land use types decreased significantly (P < 0.05), but soil bulk density increased significantly(P < 0.05). Soil alkaline hydrolysis of nitrogen in all plantations decreased obviously, whereas soil total phosphorus, soil total potassium, and slowly available potassium increased significantly(P < 0.05) during the conversion. With increasing of land use intensity, the soil quality decreased significantly(P < 0.05). The soil quality indexes of SF, AP, RP, and RAP decreased by 63.4%, 85.8%, 81.2% and 84.1%, respectively, compared with that of PF. However, there were no differences in soil quality among the plantations. The litter fall, canopy density, root length density, and fine root density had the positive and significantly correlations with the soil quality index(P < 0.05). Moreover, fine root density had the largest direct effect on soil quality, and litter had the largest indirect effect. Our results suggested that the transformation of tropical primitive forests to rubber and areca plantations significantly changed soil properties and soil quality, which was mainly explained by the plan community functional traits of fine root density and litter fall. Improving the management of litter fall and understory plant community, which influences fine root density, will help increase soil quality in plantations in tropical region.