A software-defined data center (SDDC) and a service cluster scheduling and traffic monitoring method therefor. A software defined networking (SDN) controller implements a scheduling and decision function of load balancing. As a load balancer, the SDN controller follows a serving node load balancing principle, and customizes a packet forwarding flow table to instruct an edge switch to direct user traffic to a specified serving node. The SDN controller may monitor load of a serving node in a service cluster, execute a load balancing function of the load balancer according to a load monitoring result, and select a target virtual machine. Using the SDN controller as a load balancer, a dynamic expansion capability of the SDN may be multiplexed at a control layer, and a network resource of the SDN network may be multiplexed at a network forwarding layer. Implementation complexity is low, and investment costs are low.