A Canny test calculation method was proposed based on ultrafuzzy sets aiming at the test problems of the pepper edges on the pepper pictures. The algorithm chooses RGB color model, conducts the image preprocessing with median filter first, then carries out the edge detection for pepper image by using the Canny detector based on the threshold value of ultrafuzzy set, and finally enhances the pepper outline with the morphic erosion and dilation. The experimental result shows that the algorithm can effectively detect the pepper image edge.