Embodiments of the present invention provide a method for implementing P2MP multicast, a network node, and a system. The method includes: acquiring, by a network-side leaf node, an mLDP label of a downstream user-side leaf node and FEC information from an mLDP mapping message of the downstream user-side leaf node, then sending an mLDP mapping message that includes an mLDP label and the FEC information, to an upstream network-side root node, and generating a forwarding entry; searching for or establishing an RSVP P2MP LSP, allocating a label to the FEC information, and associating a forwarding entry of each network-side leaf node with the label of the FEC information; and sending an mLDP label of the network-side root node and the FEC information to an upstream user-side leaf node, and associating the mLDP label with the RSVP P2MP LSP and the label of the FEC information.