The invention relates to a numerical control milling tool capable of reducing deformation of a workpiece. The tool comprises a platen, a moving rack, an electric slide block and a milling mechanism. The moving rack is mounted at the upper end of the platen, the electric slide block is mounted at the lower end of the moving rack, the milling mechanism is mounted at the lower end of the electric slide block and comprises a driving moor, a driving connecting part, a knife handle, a milling cutter and a cooling branch chain, the driving connecting part comprises a connecting cap, a compacting rack, an auxiliary motor and an auxiliary rod, the cooling branch chain comprises a rotating block, a liquid spraying barrel, a liquid outlet and a liquid storage device, the liquid storage barrel comprises a barrel body, a piston rod, a reset spring and a shielding sheet. Most parts of the milling mechanism are connected detachably, so that the parts are detached and maintained conveniently. In the milling process, the cooling branch chain can reduce the temperature of the milling cutter, can reduce the thermal deformation degree of the workpiece as a result of too high temperature, and improvesthe processing quality.