String matching has always been an attainable problem for the developers. The problem of string matching became vast if the length of the String to be matched is large. To solve this problem many string matching algorithm has been proposed by many of the developers. Rabin - Karp algorithm is one of the strongest algorithms proposed for string matching by the researchers. In this paper, the authors will Study the Rabin Karp algorithm that provides a better average running time by using the hashing algorithm for string matching.