Edge detection of image is one of the most elementary techniques in the field of the image processing and vision computing. Main methods on image edge detection are researched in this paper. Firstly, the classic methods of image edge detection are introduced. Secondly, the technique of linear filter and its application is discussed. At last, wavelet, which has multi-scale method, is researched and applied to image edge detection, some good results are gained correspondingly. At the same time, co...