Abstract: To solve the problem that usual edge detectors are inefficient when applied to SAR image because of the multiplicative speckle noise, a novel SAR image multiscale edge detection method based on DS evidence theory is proposed.This method uses DS evidence theory to fuse multiscale ROA operator responses.And detection uncertainty is introduced in fusion procession.Basic probability assignment function(BPAF) is designed based on the relationship between the probability of false alarm and detection threshold,which detection uncertainty reaches maximum value at the detection threshold.It is shown by detection results and diagrams that uncertainty of edge detection is reduced effectively.