A network service management method, wherein the method comprises: receiving, by a controller, a service level agreement that is signed by a software-defined networking in a wide area network, SD-WAN, user and that is sent by a network management server so that the controller provides a service for a terminal corresponding to the SD-WAN user based on the service level agreement signed by the SD-WAN user, wherein the service level agreement comprises an identifier of the SD-WAN user, at least one service class and a service level, wherein each service class corresponds to a different service level, wherein when a service level agreement signed by the SD-WAN user for different flow types includes a plurality of different service classes, the controller provides different transmission paths for the different flow types based on the different service classes signed by the SD-WAN user; receiving, by the controller, an access request message that is of a to-be-served flow and that is sent by a network device, wherein the access request message comprises an identifier of the to-be-served flow and an identifier of a terminal that corresponds to the SD-WAN user and sends the to-be-served flow; determining, by the controller, service level information of the to-be-served flow based on the identifier of the terminal and the identifier of the to-be-served flow; determining, by the controller, a transmission path of the to-be-served flow and a transmission path of a being-served flow based on the service level information of the to-be-served flow and service level information of the being-served flow, wherein the to-be-served flow is a flow to which no network path is allocated, and the being-served flow is a flow to which a network path is allocated; and publishing, by the controller, the transmission path of the to-be-served flow and the transmission path of the being-served flow to the network device. receiving, by a controller, a service level agreement that is signed by a software-defined networking in a wide area network, SD-WAN, user and that is sent by a network management server so that the controller provides a service for a terminal corresponding to the SD-WAN user based on the service level agreement signed by the SD-WAN user, wherein the service level agreement comprises an identifier of the SD-WAN user, at least one service class and a service level, wherein each service class corresponds to a different service level, wherein when a service level agreement signed by the SD-WAN user for different flow types includes a plurality of different service classes, the controller provides different transmission paths for the different flow types based on the different service classes signed by the SD-WAN user; receiving, by the controller, an access request message that is of a to-be-served flow and that is sent by a network device, wherein the access request message comprises an identifier of the to-be-served flow and an identifier of a terminal that corresponds to the SD-WAN user and sends the to-be-served flow; determining, by the controller, service level information of the to-be-served flow based on the identifier of the terminal and the identifier of the to-be-served flow; determining, by the controller, a transmission path of the to-be-served flow and a transmission path of a being-served flow based on the service level information of the to-be-served flow and service level information of the being-served flow, wherein the to-be-served flow is a flow to which no network path is allocated, and the being-served flow is a flow to which a network path is allocated; and publishing, by the controller, the transmission path of the to-be-served flow and the transmission path of the being-served flow to the network device.