Based on the two-center nonvolatile holographic recording method and the theory model combining band transport model with the two-dimensional coupled-wave equations, the numerical simulation method is used to study the photorefractive formation and diffractive properties of the crossed-beam photorefractive gratings. The influence of the intensity change of sensitizing ultraviolet (UV) light and the total intensity change of the recording red light on nonvolatile crossed-beam photorefractive gratings in LiNbO3:Fe:Mn crystals is investigated. And the results, including the average refractive index modulation, the spatial distribution of the diffracted intensity and the diffracted efficiency at the fixing end, are obtained. When the UV light intensity increases under fixed red light intensity, the average refractive index modulation increases accordingly, the spatial distribution of the diffracted intensity is almost unchanged and the diffraction efficiency increases firstly and then decreases. There is an optimal intensity for the sensitizing UV light to achieve the maximum diffraction efficiency (higher than 80%). When the intensity of the sensitizing UV light is fixed, with increasing recording red light intensity, the index grating recorded wears off, the spatial distribution of the diffracted intensity is more and more homogeneous, and the diffraction efficiency decreases.