The invention discloses a method and a device for multicast users of a specific source group to leave quickly, which are used for solving the problem of multiply increased delayed and slow leave, which is caused by the resolution of a query message of a specific source group, of part of multicast users of a specific source group. In the method, a reserved field in a conventional membership report message is used and a special membership report message is introduced to instruct the construction of the query message of the specific source group, so that the prioritized query and quick leave of users of the specific source group in a large scale IP multicast network are ensured. When the method and the device are used for the optimized control over a high-bandwidth multicast group, a frequent joining and leave multicast group, high-priority users and the like, the congestion of the multicast network can be reduced, the network performance and safety can be improved, the user friendliness and performability, maintainability and manageability of the multicast service can be strengthened and the multicast source server can be protected to a certain extent.