Abstract: Current methods exist some problems of obtaining the lighting information that whether the ray is direct light and whether its irradiance reaches or exceeds a certain value. In order to solve the problems, an image-processing method based on Matlab was proposed. By processing the light-shadow images, the lighting information was acquired by this method automatically. Relationships between the characteristics of light-shadow images and the lighting information were analyzed. And some grid images under laboratory lighting conditions were taken. Meanwhile, Matlab program was designed and applied to get the corresponding lighting information of the images. The results showed that this method could obtain the characteristic values of light-shadow images and actual lighting information accurately, and the program run stably.