Considering the low contrast, fuzzy edge of infrared images, an enhancement algorithm based on the luminance and contrast masking characteristics of the human visual system is presented, the parametric contrast is computed, then non-linear gain function is used to process the parametric contrast, which enhances low contrast more than high contrast, to improve image details and image contrast, then to suppress small coefficients by threshold denoising method. The incomplete beta function is applied to improve global brightness of image. Experimental results demonstrate the ability of the proposed algorithm to achieve simultaneous local and global enhancements. The phenomenon of over-enhancement is avoided. The enhanced image is of good visual perception.