With the rapid development of information technology， the problem of computer network security is becoming more and more serious. Network attacks， data leaks and other security incidents have brought great threats to personal privacy and national security. Based on this， various circles have explored and studied a variety of network security defense technologies， of which big data and artificial intelligence technology is one of the hottest technologies today， and is widely used in the field of network security. This paper aims to discuss the application of these technologies in computer network security defense system.