Abstract: A fast convolution based cell averaging constant false alarm rate(CCA-CFAR) detector based on convolution for target detection in synthetic aperture radar(SAR) images is proposed in this paper. As a first step, the statistic matrices of the SAR image are computed according to the background clutter distribution model. Then, a convolution model is built for the CA-CFAR detector to realize the moment estimation, and background clutter distribution function of all pixels can be obtained. Finally, the detect threshold for each pixel is calculated to determine whether the pixel is the target point. The algorithm has the advantages of low complexity and high computational efficiency, and can achieve SAR image real-time target detection. Experimental results demonstrate the effectiveness and usefulness of the proposed algorithm.