We present a vortex phase retrieval method based on liquid crystal spatial light modulator. It's different from traditional phase retrieval method. In this method, a liquid crystal spatial light modulator is used to show the optical vortex phase, and a CMOS camera captures the donut image. A modified GS algorithm iteratively calculates the target phase with a random phase input and amplitude before LCD surface. The procedure recovers the vortex phase after several iterative calculation and it is confirmed that the method can be workable. Finally, we calculate the system optical aberration and quantitatively analyze the aberration by using Zernike decomposition.