Liquid crystal on silicon (LCoS) based spatial light modulator (SLM) is widely used in research areas such as holography display and optical measurement. However, a certain aberration term to the incident wavefront is introduced due to the curvature of the LCoS backplane, and the correction of this phase aberration is important to improve the accuracy of phase modulation by the SLM. In this paper, we propose to use several phase retrieval techniques to measure the corresponding wavefront directly and employ the obtained wavefront to correct the aberration introduced by the curvature. An interferogram acquisition technique based on the self wavefront modulation of SLM is proposed. Besides, a method for determining the corresponding active area of the LCoS backplane and parameters of 2-D projective transformation is proposed to transform the active area to the fitted resolution of the SLM. A RMS value to approximately λ/32 after correction is achieved.