A cup-loading device for planting cups includes a profile bracket, a horizontal driving mechanism, a pressing mechanism and a planting cup grasping mechanism fixed at an output end of the pressing mechanism, wherein the horizontal driving mechanism and the pressing mechanism are disposed on the profile bracket, an output end of the horizontal driving mechanism is connected to the pressing mechanism so that the pressing mechanism move horizontally along the profile bracket, and the planting cup grasping mechanism includes a plurality of mechanical clamping jaws and a guide device for adjusting a spacing between adjacent mechanical clamping jaws. The pressing mechanism moves to the arranged planting cups, the planting cup grasping mechanism is pushed downward to touch the planting cup, and then the planting cups are arranged at equal distances on the planting cup grasping mechanism, and then accurately fill in the planting plate.