This paper proposes a new algorithm based on gradient similarity (GSIM).By comparing the original images with the disturbed ones on their luminance contrast and resolution an image quality assessment index system was obtained and a modified GSIM was constructed.Comparison experiments show that the correlation prediction accuracy and consistency of the proposed metric are respectively 8.5% 7.6% and 4.8% higher than the PSNR index and are respectively 1.5% 3.8% and 2.6% higher than the SSIM index.In terms of experiment results, the new algorithm shows better feasibility comparing with MSE PSNR and SSIM image quality assessment methods.GSIM can overcome the influence of the difference in background intensity and it is efficacious to reflect the laser-dazzling effect.