In order to improve calibration accuracy of the liquid crystal spatial light modulator (LC-SLM), strip grating phase image were proposed to calibrate the LC-SLM. Firstly, the relation between the phase contrast of the strip grating and the intensity of the zero-order diffraction spots was simulated based on Fourier optics. Then the experimental optical path was set up and the strip grating phase image was loaded on the LC-SLM to measure the relation between the gray level and the intensity of the zero-order diffraction spots. Through calculation and analysis, the relationship between the gray level and the amount of phase delay was obtained. And finally, calibration LUT file of LC-SLM for 488 nm laser was also obtained. After calibration, a higher linearity of 0.996 4, and a lower calibration error of 0.224 0 rad were got. The experimental results show that, the double-helical spot generated by the complex high-order phase was basically consistent with the simulation results when the LUT was presented on LC-SLM. The results show that for a specific wavelength, LUT file can be obtained by calibration of LC-SLM by using the strip grating phase image and the beam can be modulated effectively according to the loading phase image, and the method is simpler.