In order to evaluate the influence of laser intensifier to the performance of the image intensifier, the irradiation experiment of continuous laser to the image intensifier is carried out and the influence of laser irradiation on the gain characteristics of the intensifier is analyzed. Experimental results show that with the increasing of the incident laser power, the image intensifier is gradually developed to the surface saturation by the point saturation, and the diameter of the saturated spot is linear with the cube root of the incident light intensity. The laser illumination required for the point saturation is about 1.64 μW/m2 and the laser illumination required for the surface saturation is about 1 371.9 μW/m2. The maximum laser illumination allowed for the linear gain of the image intensifier is about 8.95 μW/m2, which indicates that the point saturation pre-image intensifier is in a linear gain state. With the increasing of the incident laser power, there is no crosstalk between the pixels of the image intensifier, which indicates that the gain saturation of the image intensifier appears, and the output light intensity is strongly affected.