Considering the programmable phase modulation ability of liquid crystal spatial light modulator (LCSLM), the implementation of phase grating wavefront curvature sensor based on LC-SLM is introduced. A closeloop phase retrieval method based on eigenfunctions of Laplacian is proposed, and its accuracy and effective range and stability are analyzed through numerical simulation. The simulation results show that comparing with the open-loop phase retrieval method the close-loop phase retrieval method has a higher accuracy and a larger effective range. Moreover, the close-loop phase retrieval method is stable regardless of modal cross coupling.