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.