In this method,big-scale wavelet was used to detect main profile of the target and to restrain noise and sharp edges of background,and edge detection with precise location of the image was performed with small-scale wavelet,meanshile,two adaptive thresholds were calculated respectivly,two edge maps at each bigger threshold were performed logical-AND operation,short discrete edges were taken out from the result edge map,the remained edges with similar amplitude and phase were connected according to the edge map at smaller threshold and the phase map of big-scale wavelet edge detection,at last,closed profile of the target was gained.Experiments turned out the algorithm works efficiently.