In view of the low illumination environment, the image quality is reduced to different degrees due to insufficient brightness, which affects the usability of the image. The paper proposes an image enhancement algorithm based on improved homomorphic filtering and histogram equalization. Firstly, sigmoid function is used to construct a single parameter homomorphic filter function which can not only guarantee filtering effect but also reduce adjusting parameters, so as to correct the effect of uneven illumination. Then, an contrast-limited adaptive histogram equalization algorithm is applied to enhance image in HSV space. The experimental results of subjective observation and objective evaluation show that the improved algorithm can optimize the effect of lighting inhomogeneity on the image, enhance the contrast of low light images, and make the processed images more visible.