Face to DDoS attacks, an effective defense scheme based on SDN for DDoS attacks is proposed in the paper. The proposed scheme includes an attack module, a monitoring module, and a defense module. In the attack module, DDoS attack scenarios are simulated in Mininet by producing the attacking traffic. Then, in the monitoring module, sFlow technology is used to monitor and extract common attack traffic characteristics. Besides, in the defense module, DDoS attack defense is implemented with API in the ONOS controller. Furthermore, when the traffic exceeds the threshold, the speed is limited to prevent the network from being paralyzed, and the traffic type is categorized into attack, ordinary, or business traffic. Then, after DDoS defense is performed, the speed limit is restored, and the QoS rules are used to ensure the forwarding of business traffic. The simulation results demonstrated the excellent performance of the proposed SDN-based solution for defending against DDoS attacks.