Abstract.With the advent of the Internet era, the network has been widely used in production and life, and network security has become a hot topic. Nowadays, the traditional prevention technology is difficult to prevent the various increasing network attacks. There is an urgent need for a complex network intrusion detection technology to ensure the normal use of the network. According to the above problems, this paper studies the problem of network intrusion detection technology in dynamic and complex background. This paper introduces the network intrusion detection technology under dynamic background, and expounds the basic idea of detection, detection system model and packet capture device of detection system, and then analyzes the technical advantages of the detection system. the experiment proves that the network intrusion detection system can detect intrusion quickly and accurately to prevent intrusion.