Abstract: The traditional network is increasingly difficult to face the complex network structure, so a new network architecture is born, namely software defined network (SDN). The service flow of SDN data center mainly includes long stream and short stream. The long stream has the characteristics of long duration, insensitive delay and high bandwidth demand; while short flow has short duration, high delay sensitivity and low bandwidth requirement. Short flows account for less than 20% of the total traffic, but the number of traffic bars is about 80% or more of the total traffic; long flows account for more than 80% of the total traffic, but the number of traffic bars is less than 20% of the total traffic. It is found that the long flow is often ahead of the short flow in the outgoing port queue, causing the short flow to wait for a long time, which is very likely to cause network congestion. The design proposes a queuing mechanism and a route optimization guarantee mechanism based on the characteristics of the two service flows, setting the short flows as high-priority queues, which are prioritized and scheduled by the SDN controller; setting the long flows as low-priority queues, while using a route guarantee algorithm for compensation. The routing assurance algorithm first removes the links that do not meet the bandwidth requirements of the long flows, and then calculates the shortest delay path. In order to improve the efficiency of the algorithm of this design′ FPGA and 10G ethernet are used to simulate the service flow in SDN, and simulate on FPGA to verify the advantages of this design for the optimization of network delay, bandwidth and FPGA parallel computing.