Abstract: The fast attenuation algorithm of laser intensity is presented in this paper to shorten the time of precisely adjusting attenuation rate. The accurate adjustment of attenuation rate is determined by both the current attenuation rate and the maximal gray level of practically sampled spot image. When the collected spot image was distorted by the saturation of the optoelectronic receiving device, the light spot image could be dealt with by removing the saturated portion of the light intensity information and simulating by tree-dimension Gaussian fitting based on the least squares method. Then the real distribution and amplitude of the laser intensity could be restored. If the attenuation rate is very large, the present amplitude can be obtained directly. The appropriate attenuation adjustment rate can be calculated based on the real distribution and amplitude of the laser intensity. Laser intensity was adjusted fast and accurately. The validity of the fast attenuation algorithm was testified by the experiment of CCD and stepper motor-driven double wheels attenuator.