Abstract: The Yunnan Observatory has decided to develop a Remote Observing System for its 2.4m telescope.As the Remote Observing System will communicate through the Internet,it will face many threats from the Internet.Because of an earlier project design,the current network for the telescope only includes simple protective measures.In order to guarantee the network security and avoid all unsafe factors causing the loss,this paper gives a design of a secure network structure based on the analysis of the current network.The new structure follows the DMZ design scheme.It has separate public servers and an internal network.The measures further safeguard the internal network.We also construct a firewall for the network with a function of intrusion detection which makes the detection of packets more thorough.The firewall allows the supervision of any unauthorized activity from the inside. The new network for the 2.4m telescope is thus provisionally secure.