The pure phase type of spatial light modulator (SLM) is a widely used high precision optical device. The double-hole interference method recommended by Holoeye can correct the phase to a result which has 80% of 1st diffractive efficiency for 16 level blazed grating. But the total process needs to be conducted carefully with filtering collimation, beam expanding etc., and it takes too long time. The diffractive method using binary grating can simplify the correction process. We make a measurement just every 10 gray level. The total 256 values are achieved by interpolation using Matlab. As a result, the 1st diffractive efficiency of 16 level blazed grating and binary grating reaches to the Holoeye catalog values of 83% and 40% respectively. The experiments prove that the diffractive method based on the stable averaged phase modulation of Holoeye Pluto SLM can correct the characteristic of SLM with simplicity and feasibility, and it is not limited by the phase flicker under 5-5 sequence configuration of SLM.