A method for fixing an initial brightness level of lights is provided. Gamma correction is performed on the light based on a dynamic Gamma curve. When a user adjusts brightness of the light based on the dynamic Gamma curve, a dynamic Gamma curve image is valid all the time when a set current brightness level n changes from 0 to N, and when x>0, the dynamic Gamma curve image is continuous, and accordingly, brightness of the light continuously changes gradually. Further, by calculating an initial brightness PWM critical duty ratio D of light sources, the dynamic Gamma curve is customized according to the light, so that an initial brightness level position of the light sources in the same model is fixed and unified.