Abstract: In RoboCup 4-legged league,variation of lighting conditions greatly affects the result of image processing.In order to solve the problem,this paper analyzes how the color of image taken by the vision sensor varies along with lighting intensity,and presents a method of color-space transformation based on electric field model,through which color images remain consistent in spite of lighting intensity variation.Experimental results show that image processing based on the transformation has greater adaptability to lighting conditions.