In the process of synchrotron radiation X- ray imaging, the X- ray image with lower or uneven contrast is obtained invariably, this causes some details of the sample in the image are difficult to observe and analyze. In order to solve the problem, a new algorithm is proposed to enhance the X- ray image and get a higher contrast. The algorithm is based on homomorphic filtering, and combined with image denoising pretreatment and gray level adjustment, so that the contrast can be enhanced and the image quality can be improved simultaneously. Furthermore, the algorithm is realized by writing program, and the X- ray images of a resolution target and marine fish are utilized to test the performance of the proposed algorithm. The results show that the proposed algorithm can well enhance the low contrast X-ray images with uneven distribution of gray level, and show the sample detail information more clearly, the gray level distributes more equably. Concurrently, the effect of X-ray image denoising is obvious.