Abstract: In order to measure Stokes vectors simply and conveniently, a dual-photoelastic-modulator working at different frequencies was adopted to generate high frequency modulation component loaded with the parameters to be measured after light modulation because of the frequency superposition. Four Stokes components suitable for all polarization measurements were obtained once through a phase-locked polarization measurement. After theoretical analysis, simulation verification and error analysis, the effects of phase delay and incidence angle on the measurement results were studied. The results show that all the measured polarization components can be obtained with only one measurement and the method provides theoretical support for further engineering implementation.