A Multipoint Control Unit (MCU) cascaded system is provided, which includes a plurality of MCUs under the management of a service management center. The cascade manner between the MCUs in the system is a reticulated cascade. A communications method for an MCU cascaded system, an MCU, and a service management center are also provided. In the embodiments of the present invention, because the connection and networking mode of MCUs in a cascaded system is changed, a transmission path passing the least MCUs can be selected according to a connection situation between the MCUs. Therefore, transmission delay and decrease of video and audio quality due to multiple forwarding by MCUs can be effectively avoided, and thus the media stream transmission time is reduced, and the play quality of the media stream is guaranteed in an overall manner.