The side-look imaging of SAR （Synthetic Aperture Radar） may result in the pockety density

so we can not get a satisfying result by using CFAR （constant false alarm rate） detection on the whole image. To improve the oil detection capability

we propose a new oil detection method based on edge detection in this paper. First

the AOI （area of interest） of oil is detected through radio edge detection

then an improved Weibull-CFAR detector is applied to the AOI. Comparing with the whole CFAR detection results

this detection method demonstrates better accuracy and efficiency on SAR images with pockety density

especially suitable for the oil detection of big images.