The path-wise technique of test data generation is a high-efficiency technique for test cases generation, implements test data generation by building and solving constraint systems. However, most of path-wise generation techniques only take the control dependence among statements into consideration, viz, build constraint system by analyzing the control flow graph but neglecting the data dependence among statements. Considering both of them, this paper proposes a new domain reduction method for improving the test data generation technique of domain reduction. Experimental results showed that this method improves the successful rate and execution efficiency of test data generation at a large extent, although it couldn’t find the optimum solution for test data generation.