详细论证了峰值信噪比（PSNR）在网目调数字图像质量评价中的缺陷，并对PSNR算法进行了改进，提出了分块的峰值信噪比（BPSNR，Block PSNR）这一方法，降低了PSNR对图像阶调分布的依赖性，提高了评价结果与视觉感受的一致性。实验证明，这一方法可以用于网目调数字图像的质量评价。

The disadvantages of PSNR in digital halftone image’s quality evaluation were demonstrated. Algorithm of PSNR was improved and blocked PSNR was put forward to decrease the dependence of tone distribution and increase the consistency between evaluation result and people’s visual recept. Experimental result showed that method is available in evaluation of digital halftone images.