Aiming at the characteristics of the infrared image and the insufficient of traditional histogram equalization enhancement method, an improved histogram equalization method is proposed． Firstly, each gray level histogram of the infrared image are adjusted using the proposed weighted function, wherein the low gray level histogram of the background region is reduced, while the high gray level histogram remain unchanged, and then the equalization processing are done． The experimental results show that, the proposed method effectively suppresses background noise and improves target contrast． The overall performance is better than traditional histogram equalization and dual platform histogram equalization method．