This paper aims at finding an algorithm in wireless sensor and actor networks (WSANs) to recover the failure actor. First, this paper describes the real-time coverage model in WSANs, proves WSAN's coverage recovery is NP-hard. A cell-based mobile fault-tolerant algorithm HMFR is presented to recover the failure actor, which has a good performance under a limited condition of initial deployment of network. Through simulation experiments, the results show that the algorithm is more effective than the present algorithms in terms of actor coverage and move distance.