Proposes a virtual-Steiner-tree-based secure multicast routing Protocol in wireless sensor networks for the traditional Secure Multicast Routing Protocol not applying to multicast communications. Basic Random Key Scheme model has been proposed to distribute key among nodes of wireless sensor networks, and the security of this protocol has been analyzed by the multicast tree generation algorithm. The results show that the protocol enables each node share a symmetric key with its neighbor nodes, to stop the false nodes involved in the routing process for the purpose of establishing a secure multicast tree.