Abstract: The edge detection is one of the fundamental topics in the image analyses and the computer vision.Firstly the traditional operator methods are introduced.Secondly two methods，which arisen in recent years，of multi-scale edge detection based on wavelet transform and mathematical morphology are introduced.Furthermore the algorithms and performances are also described.Finally by using those images after edge detection based on the above technologies，the area of a reservoir are calculated，and the results are compared and analyzed.The result proves that the accuracy of the multi-scale edge detection based on wavelet and mathematical morphology are higher than all traditional operator methods.