paper describes a master-slave surgical robotic system with software modular system design, which integrates various independently developed surgical devices. When we add new functions to the developed modular system, there is no need for time-consuming redesign of the entire system. However, we cannot evaluate the computational system load exactly because the system configuration changes according to the components included. A master-slave system should be a stable and reliable control system with high sampling frequency to enable human visual feedback control. Moreover, it requires consistent master-slave operation on the integrated component. To maintain reliable real-time performance and consistent operation, even with changes in system configuration, we introduced a software system consisting of; A position registration system to realize consistent operation on the integrated component, modular asynchronous system to avoid performance changes caused by the introduction of various subsystems and a management system to arbitrate inconsistencies between systems. An optical tracking system is used to integrate position and motion information of the subsystems to simplify setup in an operating theater. We evaluated the feasibility of the modular master-slave system by integrating independently developed components into the system. The results of the evaluation experiments showed that we could control all the subsystems consistently as an entire master-slave surgical system on an integrated coordinate system with stable real-time response.