The standard band transport model with mobile ions and the coupled wave equation under different initial intensity ratio and fixing temperature are solved by numeric method to study the dynamics of recording and thermal fixing photorefractive hologram at high temperature in LiNbO 3 photorefractive crystal. The theoretical thermal fixing time and the temperature dependence of the space charge field are obtained. During of recording and fixing the partial cancellation of proton grating and the donor grating causes the emergency of the net charge field’s extremum, and proton grating could also change the direction of the coupling between the reference light and the signal light.