Abstract: Previous researches of robot motion planning are based on known and invariant environmental model. However, there are uncertainty and emergency in the real world. In this paper, an emergencytolerant motion planning method is presented based on topological method mainly for manipulator arms in an assembly workspace. The emergency-tolerant means that the robot can reach the goal by avoiding the unexpected obstacles. A robust and real-time emergency-tolerant topological motion planner ETTMP is thus constructed.