Abstract: The disclosure provides a streaming service system, a streaming service method and a controller thereof The streaming service system includes a plurality of switch nodes, a plurality of surrogate servers, a content management apparatus and a controller. The switch nodes are connected, and the surrogate servers are respectively connected to one of the switch nodes. The controller is connected to the switch nodes and communicates with the content management apparatus. The content management apparatus provides server information of the surrogate servers to the controller. When a first client apparatus is joined to a streaming group, the content management apparatus informs the controller. Further, the controller selects a first surrogate server from the surrogate servers, and sets at least a portion of the switch nodes to adjust a multicast tree. The first surrogate server transmits streaming packets to the first client through a first transmission route of the multicast tree.