Abstract: Aiming at the automatic test generation for character string data,this paper defines the distance between two strings.A real-valued objective function is constructed with respect to the string predicate which does not meet a given path condition,and its minimum is computed by using a speedy descent search algorithm.As a result,path-oriented string test data can be automatically generated.In addition,this paper investigates the relations among test generation effectiveness and original inputs as well as path orders processed,and the test generation effectiveness is compared with other three algorithms such as the genetic algorithm.The experimental results illustrated that this approach is more economical and effective.