Multicast distribution tree establishment method and device

The invention provides a multicast distribution tree establishment method. The method includes the steps that when a router receives group jointing messages, an outgoing interface is looked for in a unicast routing table according to the multicast source address; when the found outgoing interface is a non-PIM neighbor interface, and the outgoing interface is not bound with a logic tunnel interface, the router determines a far-end router which is provided with the minimum hop counts from a upstream router to the router and supports the multicast PIM function; a tunnel is built by the router and the far-end router, and tunnel packaging is conducted on the received group jointing messages and is sent to the far-end router through the built tunnel, so that the far-end router can conduct building of a multicast distribution tree. Based on the same inventive concept, the invention further provides a multicast distribution tree establishment device, in the network containing the router which does not support the multicast PIM function, establishment of the multicast distribution tree can be achieved.