Taking the crustal velocity structure model as constraints, the authors acquired the crustal density structure model of Qiongdongnan Basin by forward fitting the Bouguer anomaly distribution. Then, after temperature-pressure correction of crustal density model, the authors combine the crustal velocity model and high temperature and pressure experiment results of the most common rock composition, to infer rock composition of the upper crust of five depressions in Qiongdongnan Basin. The results show that crustal rock density exhibits strong vertical and horizontal heterogeneity in Qiongdongnan Basin; the spatial variation of rock density is closely related to the structure pattern of alternate depressions and uplifts.