The niche theory predicts that soil resource heterogeneity promotes species coexistence because of reduced competitive exclusion among species, while the neutral theory predicts that species coexistence is more strongly determined by stochastic processes. To study the relationship between soil resource heterogeneity and tree diversity, 16 plots of 1 hm² area each were randomly set up in Xishuangbanna tropical seasonal rainforest, southwest China. This forest is characterized by abundant tree species and complex community structure. The laterite soil developed from siliceous rocks, and the average rainfall is 1493 mm. We investigated the tree diversity of each plot and analyzed the coefficient of variance (CV) of AN (Ammonium Nitrogen), EP (Extractable Phosphorus), EK (Exchangeable Potassium), OM (Organic matter), pH, TN (Total Nitrogen), TP (Total Phosphorus), and TK(Total Potassium) to show the relative heterogeneity of soil nutrients. We divided the 1hm² plot into 25 quadrats, each with an area of 400 square meters (20 m ×20 m). All four corners of each quadrat were set as sampling points. After the litterfall was cleared from the soil surface, we collected 500 g soil at 1-10 cm depth under the soil surface for soil nutrient analysis. The soil nutrient content in each 20 m ×20 m was calculated as the mean of the samples taken from the four corners. We calculated the CV of the soil nutrient in 25 quadrats to show the relative heterogeneity within a 1hm² plot. We randomly selected five 20m ×20m small quadrats in a 1hm² plot for tree evaluation and all the trees with a DBH (diameter at breast height) above 1cm have been investigated. The trees within five quadrats were summarized to show the relative levels of tree diversity within a 1hm² plot;besides, voucher specimens were made for all trees which surveyed in all of the 16 plots with each area of one hectare and conserved in Laboratory of Plant Phylogenetics & Conservation Group, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences. We used Pearson correlation analysis to explore the correlations between soil nutrient heterogeneity (indicated by the CV of each soil factor within a 1hm² plot) and tree diversity (indicated by tree richness, the Shannon-Wiener index, and the Pielou evenness index within a 1hm² plot) in the Xishuangbanna topical seasonal rainforest. Before the analysis, the K-S (Kolmogorov-Smirnov) test was implemented to inspect the normal distribution of all variables. The results showed that all variables (CV of soil factors and tree diversity) followed a normal distribution (P > 0.05), which was suitable for Pearson correlation analysis. A significant positive correlation was found between the CV of TK and tree diversity (tree richness, Shannon-Wiener index) (P < 0.05), indicating that potassium heterogeneity promotes tree coexistence and niche differentiation among trees based on potassium utilization. OM and AN were positively correlated with the Pielou evenness index (P < 0.1), indicating that the heterogeneity of these nutrients moderates competitive exclusion among trees and promotes tree coexistence. Except for TK, no significant positive correlation was found between nutrient heterogeneity and tree diversity. The heterogeneity of these nutrients may have relatively small effects, and the neutral or other ecological process may weaken the effects of the nutrient spatial heterogeneity on tree diversity. Our study showed that soil nutrient heterogeneity may promote the coexistence of trees to a certain extent, and that the neutral process should be considered when studying community assembly in Xishuangbanna tropical seasonal rainforest.