Network security is one important factor that affecting the performance and functions of a communications network. The construction of the network security system for Qingdao Meteorological Service is introduced from the following aspects: the redundancy of the communication line， the central unit of heat backup, the application of network security devices, safety control strategy, and the regulations of user and administrator security management. The implementation of key technologies, such as firewall configuration, the hot standby of the core switch, and the access control of the key server, is described in detail. Some suggestions are presented for the construction of the network security systems for the citylevel meteorological services.