Abstract: According to the structural characteristics of embedded software, this paper try to fit a practical function-path method of embedded software testing.By analyzing the node predicates and function constraints on the function paths, the author use a simple, fast algorithm to build up and solute a restraint system of input variables, generating function-path test cases.Practice has proved that the test cases can test the functions and structures of embedded software at the same time.The high-efficiency, low price and more comprehensive of the test cases can lower the costs of the development, testing and maintenance of embedded software.