For the purpose of preventing illegal device connection and data from being tapped, further improve security and reliability of industrial Ethernet bus network system, the paper puts forward a simple and effective security protocol. This protocol can implement to equipment identity authentication and key agreement for data encryption. The protocol is based on challenge/response mechanism, determine the legitimacy of the equipment by use of dynamic password authentication, and use the key table for key agreement. Finally, the efficiency and security of the protocol is tested and analyzed. The test results show that the protocol can complete mutual authentication and key agreement in a relatively short period of time, at the same time, will bring larger improvement to the industrial network security.