Software test is a very important phase in software development, and an important means to ensure the software?s reliability. Path-oriented testing is a main approach in software test. In this paper, an automated test data generation method for linear approximation of bifurcation function is proposed. Combined with predicate slice and Definition-Use-Control (DUC) expression of function, an innovative algorithm for path-oriented testing and automated test data generation is designed. This new algorithm, incorporating DUC expression, can determine whether the sub-path is feasible from the source point. It can also effectively decrease the adverse influence of infeasible path to the algorithm performance. Analysis shows, compared with other existing algorithms that utilize the minimization of bifurcation function method only, that this new algorithm can decrease the number of test cases considerably and increase the test efficiency.