Abstract: In order to better understand the mechanism and characteristic of foreland basin evolution in the NanSha trough, we studied the structure, sedimentology and other characteristics of the basin based on the geophysical data of the past decades collected from South China Sea Institute and recent research progress both at home and abroad. An elastic lithospheric plate flexure model for Nansha Trough foreland basin is established. The finite difference method was used to simulate the basin evolution since Middle Miocene. With the model, we reconstructed the history of deposition, subsidence, tectonic movement and deflection and deformation process in the basin, and predicted the geometry, gravity anomaly, sediment thickness of the basin in different stages. The predicted gravity anomaly and basin topography fit well with the measured data at 0 Ma stage. And the basin simulation shows that basin deflection caused by the sediment load is only about 2 300 m, indicating that the basin crust had been flexible before the formation of foreland basin, and the flexural deformation of the foreland basin is not only related to basin structure, topography and depositional load, but also possibly affected by lithospheric load in the deeper part.