Abstract: The traditional Canny operator requires human intervention，does not have the adaptive ability themselves in the variance of the Gaussian filtering and the lag threshold.The variance of Gaussian filter affects the edge preserving and de-noising effect.Different scale morphological filter replaces the Gaussian filter，can not only reduce the noise impact，but also maintain the edge strength and details.The lag threshold affects the strength of the fake edges and the continuity of the real edges.Otsu threshold and its extension to the situation that the histogram has multiple peaks，can select the favorable threshold with the image own characteristics，so that the edge detection is more continuous and reduces the presence of fake edges.