In order to solve the problems of over enhancement and performance degradation in image enhancement, an image enhancement algorithm based on the local brightness average and global contrast of image is proposed. The algorithm controls the local contrast of image according to the local brightness average of image, and adopts the local and full contrast in global part. The local contrast ratio is the gamma value of the power transformation. Firstly, the image is divided into two parts: low pass filter and high pass filter. The low pass filter controls the amplitude of high pass filter to increase the local contrast. Then′ the low-pass component is modified in a non-linear way and fused with the processed high-pass component. In the contrast experiment, the clarity of the algorithm proposed in this paper is 99% higher than that of the suboptimal algorithm, and the root mean square error(RMSE) is 16% higher. In the process of image enhancement, this algorithm can improve the definition of image, enrich the details of image, and meet the requirements of stability, robustness and high definition of image enhancement algorithm.