Robust model predictive control (MPC) is studied for a class of discrete-time singular system subject to persistent disturbance and input constrains. The notion of input-to-state stability is introduced to the model predictive control of singular systems. The design method of the singular system dual-mode MPC is proposed under the index of quasi-min-max. On the basis of the proposed dual-mode MPC approach, it can be proved that the closed-loop discrete-time singular system is input-to-state stable. Finally, the numerical simulation result shows the feasibility and the effectiveness of the proposed method.