This work aims to propose a multi-mode hybrid palletizing robot mechanism for the single-point repetitive task and multi-point flexible task in the palletizing task at the backend of the Baijiu wine box production line. The common palletizing modes in the wine box production line were analyzed. A topological structure for the palletizing robot mechanism was proposed, the transformation of the mechanism from 2-DOF mode to single-DOF mode with multiple different trajectories was realized by locking metamorphosis. Then, the kinematics was analyzed and the dimensions were optimized on the mechanism with different modes. The results showed that the motion equations of the mechanism in various modes satisfied the actual task requirements of the palletizing robot. The structure dimensions of the mechanism were optimized by dimension synthesis. The designed multi-mode hybrid palletizing robot mechanism can adapt to the changing operation trajectory requirements in the actual palletizing task, and verify the feasibility and effectiveness of the locking metamorphic method in the design of the palletizing robot mechanism.