Human-machine interaction has been being an important issue in robotics, of which master-slave control is an effective measure to control robotic execution with human's intelligence. With fixed mechanical structure and degrees of freedom, conventional master robots lack of flexibility and adaption to a variety of slave robots with different configurations, especially to reconfigurable modular robots. To overcome the shortcomings of conventional master robots, a modular master system, which we call Momas, is designed and the implementation of modular master-slave control is presented in this paper. The mechanical system is first presented. The control method, the software and hardware of the control system are then proposed, followed by the analysis of static and dynamic delay error sources of a general tele-operation architecture. A sort of independent module (joint) motion pattern on modular master-slave robot system is finally proposed as a strategy to improve position-position tracking capability. Comparative experiments are conducted to verify the advantages of the presented strategy.