Maintaining multicast information needs additional hardware overhead, and making the multicast architecture lacks scalability, thus limiting the development of multicast services. This paper applies a least interference path algorithm for MPLS in the multicast, adds multicast information table in the branch nodes MPLS, and implements the sourcetree multicast over MPLS, so  it is able to solve the difficulties of label distribution on data transmission in the MPLS multicast to achieve a good scalability. The simulation result demonstrates that the application of the least Interference path algorithm over MPLS saves bandwidth and improves multicast capability.