Improved matching algorithm of string pattern

String pattern matching is an important algorithm in intrusion detection system.Based on the analysis of two famous KMP and BM algorithms,and of the existing various improved algorithms,an improved string matching algorithm which is simple,practical and easy to understand is proposed.In this algorithm,the possible distance that a pattern backward moves is obtained through the inspi-ration of the characters of special position in the case of each mismatch of string pattern.Each of inspiration distance is calculated from the definition of a unified function,and the maximum one is taken as the actual movement distance of a string pattern shifting backward.The experimental results show that the algorithm reduce the number of times of attempts and comparisons of pattern matching and improve the efficiency of it.