Based on the TymanGreen interference system, the phase modulation character of the phaseonly liquid crystal spatial light modulator at 808 nm was studied. In order to increase the simulation fidelity of the atmospheric turbulence, the approximation method and the inverse interpolation method were used to compensate the phase nonlinearity of the spatial light modulator, and the calibration effect were compared with each other. Results show that, although the approximation method is straightforward, the inverse interpolation method can get a higher linearity of 0.991 6 and a lower calibration error of 0.06 rad. Moreover, after analyzing the calibration process and the error source, the inverse interpolation method is found to be more flexible to get a further improvement in the linear calibration, which is more significant to the pratical application of the liquid crystal spatial light modulator.