Due to the special characteristics of light in water, the information of the red channel is seriously attenuated in collected image. This causes other colors to dominate the image. This paper proposes an underwater image enhancement algorithm based on red channel weighted compensation and gamma correction model. Firstly, by analyzing the attenuation characteristics of RGB channels, the intensity and the edge information of red channel are compensated by weighting the attenuation coefficient ratio between different channels to correct the chromaticity. Then the gamma correction model is employed to stretch the intensity range to enhance the contrast which makes the image look clearer. The experimental results show that the proposed algorithm can correct the color cast effect and improve the contrast by nearly 2 times for the underwater images with too much red component attenuation.