In order to get access to the target polarization information, a new polarization measurement method of a modulation mutual difference frequency modulation is designed. In this method, The three Photoelastic Modulator (PEM) respectively work in numerical slightly in three difference frequency, polarized light is modulated to the difference frequency, and polarization information is contained in the low-frequency component. Then, through the lock-in amplifier, the four stokes polarization parameters measurement can be achieved, and Stokes parameter can describe the polarization of the light beam state. This method not only retains the original advantages of elastic-optic modulator for polarization measurements, but also overcomes the defects of the existing method which cannot use array detector effective acquisition and frequency modulation high. Moreover, the method proposed by MATLAB simulation realizes Stokes parameter measurement process. Theoretical analysis and simulation results proved the feasibility of this method.