To make space manipulators with locked joint be able to carry large load, a load carrying capacity evaluation method and a load carrying task trajectory planning strategy are proposed. First of all, the dynamic load carrying capacity analytical method and the Monte Carlo method are combined to establish the failure tolerance workspace with load carrying capacity, and it is further rasterizated into a series of cubes. Then the classic A* algorithm is improved to search the executable task trajectory; Finally, numerical simulation is carried out to clarify the effectiveness of the proposed method. The simulation results show that the failure tolerance workspace with load carrying capacity can illustrate the load carrying capacity and reachability of the space manipulator with the locked joint intuitively, and the average load carrying capacity of the obtained trajectory is 42.5% larger than the task requirement.