A method and system for improving a quality of communication based on a label distribution protocol is provided. The method includes the following: When a local label switching router (LSR) finds out a change of a route at an upstream node in a multicast label switching path (LSP), it calculates and sets up a new optimized multicast LSP according to the label distribution protocol (LDP), and delays to send a withdraw request to the upstream node in the former multicast LSP. An interruption of the data stream in the multicast LSP reconstruction procedures can be avoided or reduced, so that the loss of data packets caused by the multicast LSP adjustment is reduced, and the quality of communication of the multicast is improved.