Gupta et al., proposed a method, which is referred to as the Iterative RelaxationMethod, to generate test data for a given path in a program by linearizing the predicate functions.In this paper, a model language is presented and the properties of static and dynamic data depen-dencies are investigated. The notions in the Iterative Relaxation Method are defined formally. Thepredicate slice proposed by Gupta et al. is extended to path-wise static slice. The correctness ofthe constructional algorithm is proved afterward. The improvement shows that the constructionsof predicate slice and input dependency set can be omitted. The equivalence of systems of con-straints generated by both methods is proved. The prototype of path-wise test data generator ispresented in this paper. The experiments show that our method is practical, and fits the path-wiseautomatic generation of test data for both white-box testing and black-box testing.