One of the key features of Intranet is security. With the rapid development and wide application of Intranet, security becomes the key problem. This paper analyzes the types of traditional firewall and its main defects, introduces the principle and structure of intelligent firewall, and the proposes the realization method of network security technology under INTRANET based on intelligent firewall, which overcomes the defects in traditional firewall, and improves the safety and reliability of the network.