Abstract: The essential characteristics with greater information difference of color image are interpreted in detail.A new method to process edge detection of color image is put forward based on the differential information theory of grey system.At first,it analyses to the characteristic of pixels,and confirms differential information serial of color image.Then,it distinguishes between non-edge pixels and edge pixels through computing the differential information measure,the information entropy relative measure and the differential information relative measure.The experimental result indicates that the method of edge detection of color image has certain feasibility and validity.