Abstract: To study the performance of multicast routing, experiments are made by OPNET simulation platform. By comparing unicast routing with PIM-SM multicast routing on link throughput, the results show the obvious advantage of multicast routing on bandwidth utilization. By comparing unicast routing with PIM-SM multicast routing on network performance in four multimedia applications, including file transfer, database, VoIP and video conference, the results show that multicast routing can make different levels of improvement on delay, packet loss ratio and response time.