Abstract: In the field of indirect contrast enhancement, an S-type function based on the contrast sensitivity of human visual system is proposed, in order to overcome the limitations of traditional transformation functions under low illumination. This method models the contrast sensitivity of the human retina as an exponential function of logarithmic intensity, since there are different retinal response values for different stimulus intensities. This method uses the sensitivity model as the exponent of Steven's power law to derive a transfer function for perceived brightness. At the same time, a parameter optimization method is proposed, which maintains the average brightness of the input image, and stretches the image histogram while ensuring minimal information loss. Experimental results show that this method has less information loss and better computational complexity performance while maintaining the average brightness of the input image. It has certain advantages in existing methods in terms of contrast enhancement performance, average brightness and preservation of details.