Soil quality comprehensively represents the multiple-fold soil functions. Soil quality assessment is an important measure of sustainable soil management. This research was conducted on a tropical farm in Danzhou, Hainan, with rubber tree and other tropical fruits as main land use types. A systematic method for evaluating soil quality was adopted in which soil quality was evaluated according to the three major soil functions, i. e., nutrient availability, moisture availability and root suitability. The weight of every soil function and individual soil quality index was suggested based upon the earlier researches and the conditions of our research area. The soil quality indicators were normalized with one of the three commonly defined standard scoring functions (SSF). Based on GIS technology, soil quality of a tropical farm was evaluated and its spatial variation was presented. The result showed that the systematic assessment method based on soil function evaluat ion could comprehensively evaluate the soil quality. And with the support of GIS technology, the soil quality can be directly reflected by this method. The soils in the studied area have good water availability and root suitability while poor nutrition condition. But if properly managed, the overall soil quality condition can be improved within a short period.