Abstract: The test sequencing problem have raised a great deal of interest.Traditional test sequencing algorithms are impractical for large systems that contain more than 12 test points because of their high time complexity.Based on these considerations,the test sequencing problem is decomposed into test points selection problem and test sequence arrange problem.The test points selection problem is solved by A^* algorithm.The method of calculating heuristic evaluation function is given by using an M-ary code rule first.Then,an improved heuristic graph search algorithm A^* that can obtain all minimum test point sets is given.The test sequence arrange problem is solved by AO^* algorithm.The heuristic evaluation function of AO^* is given based on the generalization of Huffman coding.The given method is more fit for the process of DFT(design for test).Experiment and time complexity analysis show that this new algorithm can decrease the time complexities dramatically.