To investigate the performance of a reflecting 256 pixel×256 pixels phase-only liquid crystal spatial light modulator (LC-SLM) and to improve the ability of wavefront correction,the Twyman-Green interferometer and the phase-shift point-diffraction interferometer are set-up to measure the phase-shift characteristic and the static distortion of this SLM individually,and then use the SLM to compensate the distortion from itself. Experimental results show that the peak-to-valley (PV) value and the root mean square (RMS) values of the wavefront are reduced from 0.39λ and 0.08λ to 0.23λ and 0.03λ (λ=632.8 nm) respectively after applying an appropriate mapping of phase to grayscale and adding static distortion compensation. In addition,the Strehl ratios of far-field point spread functions are increased from 0.82 to 0.98. Therefore,this SLM with compensation is an excellent candidate for applications,such as dynamic diffractive optical elements,wavefront generation,high-resolution and high-precision wavefront correction.