Abstract: According to the study of the application of fuzzy technique in the intrusion detection and removal fuzzy reasoning method, the DoS attack intrusion detection system was designed and realized on the basis of removal fuzzy reasoning method. Firstly, the removal fuzzy reasoning method and fuzzy reasoning step were described. Then, DoS attack detection method using the interval and the IP address distribution change was described and so was the detection system based on removal fuzzy reasoning. The fuzzy rules for detection were made to determine network attack. Finally, the validity of the proposed method was checked by testing the method based on the removal fuzzy reasoning and the existing method with DoS attack tool and DARPA 98 dataset as intrusion detection dataset.