A paper board stacking mechanism includes a transfer platform, a front conveyor group, a rear conveyor group, an inclination device, an elevation platform, and a stop plate. The transfer platform receives and conveys cut paper boards rearward. The front conveyor group includes first and second belt conveyors. The first belt conveyor is connected to the transfer platform. The second belt conveyor is connected to the rear end of the first belt conveyor. The rear conveyor group includes third and fourth belt conveyors. The paper boards pass through the front conveyor group and the rear conveyor group to then form at least a paper board stack. The rear end of the fourth belt conveyor maintains a fixed height difference from a surface of the elevation platform on which no paper board stack is loaded or from a top end of a paper board stack positioned on the elevation platform.