To process geometrically complex special spiral rod parts, a Computer Numerical Control（CNC） system for open type lathe tailored for special spiral rod machining is designed. Taking the Industrial Personal Computer（IPC） as its basis and the movement controller GTS-800 as its core, the system hardware was established with IPC+GTS movement controller architecture, which was capable of completing such tasks as interpolation calculation, servo control, and system management simultaneously. The system software was not only adopted object-oriented and modular programming technology, but also developed the human-computer interaction interface (HMI) with a Visual Studio 2012 programming environment. Moreover, hardware and software features of the entire system could be modularized, so that various types of screw thread could be lathed. The experimental results show that the system possesses both friendly HMI and long-term reliable work system, which can meet the control requirements of the screw machining CNC lathe system.