Abstract: On the basis of the analysis and comparison of several familiar dexterity criteria,this paper presents a trajectory-planning algorithm,which improves the dexterity of the post-failure robot and resolves the incontrollable problem of post-failure robot due to too low dexterity that is brought about by the failure joint. Simulation is made on a planar robot with four degrees of freedom and experiment is done on a planar macro-micro robot with four degrees of freedom. The results show the effectiveness of the algorithm.