Abstract: Yolk color grading model was developed by machine vision. Because eggshell color is related to color message of yolk area, the difference between green-shell egg and white-shell egg was identified by means of I value using faintness method. Between yolk color grade (G) and color message (H, S, I), the linear correlativity was presented. The further research indicated that the yolk color grade was determined mainly by the H.