The PF (Poloidal Field) control system is one of the most important control systems in HT-7 Tokamak. Most of parameters such as plasma current, plasma horizontal position and plasma vertical position will be monitored. For the purpose of long-pulse discharge and the more precise control to plasma, the real-time operation system VxWorks is applied, instead of the behindhand and unbefitting DOS operation system. This paper describes the development process of HT-7 PF control system based on VxWorks on Intel X86 platforms. The method of using hardware cards in VxWorks, and the network communication with other operation systems are discussed especially. Results of the comparison between VxWorks and DOS operation systems are given too.