The general function analysis of a turning-grinding composite machine tool (TGCM) is done. The structure of the TGCM based on 'process integration with one setup' theory in this paper is presented. The CNC system functions of TGCM are analyzed and the CNC framework of TGCM is discussed. Finally the opened-CNC system for this machine tool is developed based on UMAC (Universal Motion and Automation Controller) included hardware system and software system. The hardware structure layout is put forward and the software system is implemented by using VC++6.0. The hardware system was composed of IPC and UMAC. The general control system meets the requirement of integrity machining and matches the hardware structure system of TGCM. The practical machining experiment results showed that the system is valid with high accuracy and high reliability.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.