Based on the recording mechanism of photopolymer,the effect of different recording modes on the diffraction efficiency of gratings was investigated.The existing first-harmonic diffusion model of grating formation in photopolymer was simplified,then the analytic expressions of refractive index modulation for holographic exposure,dark enhancement and uniform post-exposure were educed.The kinetics of refractive index modulation for these three recording modes under different exposure intensities were numerically simulated by using the analytic expressions.Experiments were done in a new blue-sensitized photopolymer material.The gratings were recorded by different recording modes with exposure intensities of 4 mW/cm2 and 2 mW/cm2 respectively.The results showed that if the intensity was high,the dark enhancement mode yielded to a high saturated refractive index modulation,while uniform post-exposure made the course of saturation fast.