In recent years, "WannaCry" and other ransomware network security problems have emerged in an endless stream, causing immeasurable damage to the Internet. The network intrusion detection system plays an important role in protecting the computer as an effective second gate to make up the firewall against network threats. This article firstly introduces the definition and research sta- tus of intrusion detection. Secondly, it introduces the machine learning algorithms and their general processes for solving cyberspace security problems. The specific applications of machine learning in intrusion detection are introduced, especially random forest algo- rithm, Bayesian algorithm and other mainstream machine learning algorithms in the progress of intrusion detection; finally, the de- velopment direction of machine learning algorithms in intrusion detection systems is discussed.