根据对图像加密技术的分析，提出了对加密图像置乱度进行评价的若干参数，这些参数包括：信息熵、灰度平均变化值和图像相似度。最后利用这些参数对图像加密算法进行了模拟实验分析及安全性评价。模拟试验及分析结果表明，给出的几个评价参数是实用的、有效的，可以用来对基于图像加密算法的置乱度及安全性能进行综合评价。关键词：置乱度；信息熵；安全性分析；灰度值Abstract: Based on the analyses of image encryption, some parameters such as the percentage of the information entropy, the average of pixel grey-scale values change and comparability of image are given to evaluate the image scrambling. At last using the parameters, the algorithm of image encryption is tested and the safety of the algorithm is evaluated. The simulation results of the experiment indicate that the parameters to evaluate scrambling criterion and the safety of image scrambling are useful and effective.Key words: scrambling criterion; information entropy; analysis of security; grey-scale value