Abstract: In this paper, traditional emergency communication system and cognitive radio technology are combined together.Two different-level access strategies are proposed on the premise that the primary user, the emergency user and the ordinary secondary user are sharing one spectrum pooling. A threedimension Markov chain is developed to construct an analysis model for the dynamic spectrum access of the system under these two access strategies. On the basis of this model, blocking probability and forced termination probability of emergency user and the other cognitive user are deduced. Also, the closed-form expressions of the blocking probability and forced termination probability are given and the system performance is analyzed. Simulation results show that the strategy of threelevel priority access can degrade the blocking probability and the forced termination probability of the emergency user. This strategy is able to significantly improve the performance of emergency system