This paper proposes an adaptive Overlay Multicast protocol for real-time group communication in a heterogeneous environment. Overlay multicast technology relies on end nodes by delegating the multicast functionality from routers in IP Multicast. Overlay multicast research has two major issues to consider: heterogeneous resource environment and instability of end nodes. In our protocol, data is divided into multiple layers using abstract layered data structure. The number of layers is used for the main metric to construct the multicast tree to satisfy the demand for end nodes resource environment. Furthermore, multi-path layer distribution method for fast recovery from multicast tree partition and congestion avoidance method are proposed to deal with the unstableness at end node.