For complex multi-axis or compound machine tools, checking machining processes by simulation software is needed. This paper proposed an open structure through network to obtain the process data of CNC controller. These information can be used for simulate machining process with virtual machine tool (VMT). In virtual machine tool, an open architecture is proposed, it allows for external commands to control virtual machine tool through TCP/IP. In CNC, data collector is developed with communication interface SDK of CNC, such as HEIDENHAIN Remo Tools SDK, to acquire the process data of CNC. Due to this method, simulation results of virtual machine tool is closer to the real condition. And virtual machine tool can be used more widely for various applications.