MPLS that combines the flexibility ofLayer3 routing with QoS supporting of Layer2 switch-ing is being widely developed. Unfortunately, exist-ing MPLS specification can only support unicast well,but is lack of supporting multicast. The main dif-ficulty of MPLS supporting multicast is the bindinglabels to multicast FEC. This paper mainly presentsa new scheme that MPLS supports IP multicast rout-ing protocol. In the proposed mechanism, the labeldistribution is triggered by traffic and not by controlmessages. This scheme makes the network’s scalabil-ity and dynamic characteristic better than the schemewhose label distribution is triggered by control mes-sages. The simulation results validate that this schemecan work well both in normal network and in the con-dition of higher link-loss-rate.