The crustal thickness and property in the Nansha Trough was discussed in this paper, using inverse methods for intergrating gravity anomalies in 4 seismic profiles collected by Nansha investigation team of Academia Sinica during 1987-1995. We concluded that The Crust in Nansha trough is a thinned continental crust and its thickness was reduced from Nansha microblock toward Borneo, similar to the continental margin crust thinned toward oceanic crust. The thinned trend of the crust is from ME toward SE along trough. It is most possibly oceanic crust in the end of profile 94N05. From tectonic evolution point view Nansha trough was a continental margin of antique South China Sea. Since the close of antique South China Sea and counterclockwise rotation of Borneo during Cretaceous, the crust in Nansha Trough is continental crust mostly, but still partly remined oceanic crust. Therefore, the crust in Nansha Trough is continental crust mostly, but small part remined oceanic crust in its southwest end.