Currently,the greatest number of sliding-mode control means for the under actuated two-link manipulators could not be assured of the reach-ability and robustness when all sub-sliding-modes approached one’s own sliding mode planes. It was appeared as stability of the system depended overly on selection of the parameters,and control running congested,and it was difficult to adjust the control parameters and implement. Therefore,a hierarchical nested sliding-mode control method was proposed to improve the reach ability,robustness and rapidity. Both reach-ability and stability of all the sliding mode planes were analyzed and numerical simulation of the position stabilization control of the pendubot and acrobot of the under actuated two-link manipulators was done. The simulation results show that the control means can make adjustment of the control parameters keep more continuous,and decrease the control running congestion and difficulty of the parameters adjustment,and improve effectively the rapidity and robustness when all sub-sliding-modes approached one’s sliding-mode planes.