Abstract: Aiding to the important characteristic which is “phishing” often treat somebody with the faked URI（Uniform Resource Identifier）or IRI（Internationalized Resource Identifier），this paper researches the method of estimating similarity of two characters which is the basement of similar DNS names.Studying on some researches，addresses the new fast estimation method based on overlapping after reforming.Create algorithm based on the research and develope the original software to estimate similarity of two characters.It is proved that the new method is better than ever because of the experiment result.So it is good ready for the following work of creating the similar DNS database.

Key words: similarity of two characters, anti-phishing, overlap-estimation of bitmap algorithm, network security

摘要： 针对网络钓鱼以URI（Uniform Resource Identifier）及IRI（Internationalized Resource Identifier）域名地址欺骗的主要特点，研究组成相似域名的字符相似度评估。在目前一些研究成果的基础上，提出了基于字符点阵重叠新型的快速字符相似度评估算法，并基于理论方法设计算法设计相似字符评估原型软件，得出改进前后算法的实验结果，证明了方法得到优化，从而为今后建立相似域名库工作做好准备。

关键词: 字符相似度, 反网络钓鱼, 基于字符点阵重叠评估算法, 网络安全