Abstract: In this paper, a design and implementation method was proposed for the security audit function of wireless router based on OpenFlow protocol in the threat environment such as botnet. It was designed to detect the abnormality of the router's traffic through information entropy calculation and arranged the detection system in SDN (software defined network) architecture to implement the control and display functions. The experimental results show that the entire system can detect the DDoS attack in the network, and the entire system runs only in 8 MB memory, and the network load is only 2.67%.