To address the low efficiency and high false alarm rate in detection of DDoS (Distributed Denial of Service) flood attacks,this paper proposes a DWT (Discrete Wavelet Transform) and AKD (Adaptive Knowledge Distillation) self-encoder neural network based approach to detect DDoS attacks.The approach uses the DWT to extract frequency features,the auto-encoder neural network to encode and classify the features,and the AKD to compress the model in order to achieve efficient detection of DDoS attacks.The results show that the approach has high detection efficiency for proxy server attacks,database vulnerabilities & TCP flood attacks,and UDP flood attacks,with low false alarm rate.