Abstract: On the basis of the method of critical path tracing for fault simulation of combinational circuits, the problems and difficulties in fault simulation of sequential circuits are analysed and experimented in this paper. We present a number of strategies differing from those of combinational circuits to decide sensitive input and control input, proceed critical tracing and propagate fault effect, thus generalizing the method to sequential circuits. In addition, we have made further improvement in speed and totality of the method.