It is necessary to establish a benchmark for information hiding. Imperceptibility is an important index to evaluate the performance of steganography. Based on HVS model，a new imperceptibility measure CHD for color stego image was proposed．Experimental results show that the quality of stego image calculated by CHD reflects the luminance masking

texture masking and color masking of HVS，and CHD can be used to evaluate the imperceptibility of steganography tools．