We have developed a new robot spray painting simulation system with easy-to-customize capability. In order to make it easy to customize the system according to each robot's characteristics, the main algorithms for calculation of motion were developed as a component with specific functions on the component-based software development and operation framework, called MZ Platform, which was developed by the Digital Manufacturing Research Center. As the simulation system was constructed by combining the different components, a function of the simulation can be easily changed by replacing the components. The cooperative use with other applications on MZ Platform is also possible.