The existing Internet is unable to meet the trend of merged networks, because the IP network has more complicated architecture in user-data plane, lower efficiency in transporting, and more difficulty in guaranteeing QoS (Quality of Service). SUPA (Single physical layer User-data transfer & switching Platform Architecture) is proposed by SiChuan Network Communication Technology Key Laboratory to solve those problems, and SUPANET means the network applies SUPA architecture. The SUPANET applies out-band signaling technology and can be divided into User-data platform (U-platform) and Signaling & Management platform (S&M-platform). The SUPANET simplifies the U-platform into a single physical layer, which can provide QoS guarantee for user data as well as greatly improve efficiency by QoS negotiation and Half-step Forward Switching.With the emergence of network applications, such as video meeting, remote education, multicast technology has been paid widely attention. Multicast is different from unicast or broadcast. There are several receivers, but the sender only sends one copy of data. And then the relay systems duplicate the data of demanded copies and forward the data to the relevant receivers. The advantage of multicast is not only to reduce the burden of sender and network transporting but also to raise the utility rate of network resource. Multicast has good prospects, but there are several problems in multicast, such as QoS, reliability and security. Therefore, how to integrate IP multicast network with SUPANET becomes a significant problem.In this thesis, a scheme is proposed, in which the SUPA computers act as the multicast source and the IP computers act as the multicast group members, the joining and leaving multicast group of group members and forwarding multicast data are processed by Internet/SUPANET gateway. In this model, the virtual path (VP) established by the QoS negotiation in the SUPANET can implement the fast and reliable data transporting from multicast source to multicast group members. And the key is the Internet/SUPANET gateway, which connects the two different networks. So the tasks to be accomplished by the gateway include: the transforming between IP protocols (IGMP) and SUPANET protocols (QoSNP the mapping of virtual line index (VLI), IP multicast address and gateway ports; encapsulation/decapsulation of Ethernet MAC frame and the SUPNET user data carrier: Ethernet-oriented Physical Frame (EPF). This thesis has discussed these problems above.OPNET is used to simulate the scheme for IP multicast access to SUPANET. A simplified multicast network topology structure is established, and the simulations focus on the signaling procedure, encapsulation/decapsulation and forwarding the user data. The relevant simulation results comply with the work procedure and features of multicast, and verify the validity and feasibility of the scheme.