Automatic simulation vectors generation is an efficient method to accelerate digital system’s design verification process. An algorithm that generates coverage metrics and simulation vectors for state-pair of interacting FSM is presented in this paper. Compared with FSM (finite state machines) product method and the method which treats the interacting FSM as a single FSM, this algorithm can generate accurate coverage metrics and the shortest simulation vectors. Experimental results show that this algorithm is efficient in memory usage and perfectly solves the states space exploration problem.