This paper presents the simulation and verification of programs created for the CNC Hitachi Seiki Seicos LIII lathe machine tool. The main purpose of program simulation and verification is to ensure the quality and accuracy of the cutting process, which can significantly improve production efficiency. In addition to defining the toolpath, simulation can perform linear and circular interpolation according to specific programs based on G – codes. Therefore, all the motions of the moving parts of the real lathe machine tool can be clearly visualized. The use of simulation is a good solution not only to precise the toolpath, but also verify the program and detect any possible collision between cutting tools and mobile components, before loading the program into the lathe machine tool and starting cutting processes.