A MMORPG (massively multiplayer online role-playing games) is developed based on Unity 3D. The character controller, the mouse-value interactive algorithm, the motion strategy and the AI-interaction are used to enhance the game performance. In order to improve the working efficiency of game, this paper proposes client resource forecast and synchronous reading by using coroutine technology. The strategy that uses coroutine technology in forecast reading of maps can make it possible to have long-time reading running in the spare time of the system. Experimental performance analysis and experimental results both show that the optimization method proposed can effectively reduce the time complexity of the program and enhance the efficiency of game runtime.