Abstract: In order to improve calibration accuracy of liquid crystal spatial light modulator (LC-SLM), high bit depth phase gratings were proposed. Firstly, 16bit phase grating patterns were presented on LC-SLM, and diffraction spot was generated after the modulation of LC-SLM, the intensity of the diffracted spot was measured. Through calculation and analysis, the mapping relationship between gray level signal and phase modulation was obtained. Finally, calibration LUT file (LUT16) of LC-SLM for 488nm laser was obtained. The experimental results suggest that, hollow spot of good quality can be obtained when 0~2π vortex phase and LUT16 are presented on LC-SLM. Compared with LUT8, spot quality of LUT16 is improved 1.43 times of LUT8 from 0.53 to 0.76. The results show that aiming at specific wavelength, LUT file can be obtained by calibration of LC-SLM by means of high bit deep phase gratings and that beam can be modulated effectively by LC-SLM according to the loading phase. Modulation effect is better than that of LUT8 and calibration accuracy of LC-SLM is improved.