Wireless mesh network (WMN) is a promising technology for deploying wireless infrastructure to provide wireless broadband access. High-speed wireless meshes will enable a whole new range of exciting broadcast/multicast applications, such as IP-TV and video-on-demand (VOD). There are some researches on multicast in WMNs. Ruiz et al.  study multicast tree in terms of minimizing the number of broadcast transmissions in WMNs utilizing the wireless multicast/broadcast advantage . Chou et al.  studied minimizing broadcast latency using the multi-rate nature of radio. In , a Resilient Forwarding Mesh (RFM) approach is proposed for protecting multicast sessions from link or node failures by establishing a pair of node-disjoint paths for each multicast destination. Common assumption in all the above papers is the binary packet reception model. However, in the real wireless scenario, due to the nature of radio propagation and interference, the deterministic model such as binary packet reception is not realistic. In , the authors study some multicast metrics in wireless mesh networks, such as ETT, ETX, PP, METX and SPP. However, this paper does not take reliability into consideration. In this paper, we use reliability in a probabilistic sense and we identify the reliability of a multicast session with the packet successful delivery probability from the source to the multicast destinations.