The invention provides a uniform processing method for the light irradiance of surface forming additive manufacturing system, and the method comprises the following steps: 1) establishing a xoy coordinate system on a projection plane and a mask image coordinate system to determine the positions of the pixels and the light irradiance distribution model; 2) according to the resin curing characteristics and light source properties, giving the light irradiance target value; adjusting and setting in sequence the gray value of each position so that the measured irradiance value of the irradiance at the positions of the projection plane is equal to the target irradiance value; and 3) according to the bilinear interpolation algorithm, calculating the gray value of each pixel in sequence and realizing the uniform distribution of the irradiance. The method of the invention can effectively realize the uniformization of the light irradiance in a projection plane. With fewer measurement points, the measurement method is simple; and after the interpolation calculation, the uniformization effect is obvious. The method can obviously increase the accuracy of the system and the success rate of manufacturing.