An improved heuristic algorithm is developed which can optimize the multicast routing under the condition that both delay and bandwidth are constrained. Performance analysis and computer simulation show that the routing mechanism can successfully solve the QoS problem in the case of many-to-many cast session. The scheme can make the cost of routing tree optimized and the bandwidth and end-to-end delay guaranteed. Because complexity of algorithm is limited, it is suitable to deal with networks of large size. An improved heuristic algorithm is developed which can optimize the multicast routing under the condition that both retard and bandwidth are constrained. Performance analysis and computer simulation show that the routing mechanism can successfully solve the QoS problem in the case of many-to-many cast session The scheme can make the cost of routing tree optimized and the bandwidth and end-to-end delay guaranteed. Because complexity of algorithm is limited, it is suitable to deal with networks of large size.