The utility model relates to a numerical control system, and discloses a universal level-selecting switch for an input port of the numerical control system. The switch comprises a cabinet and a circuit board. The circuit board is provided with an input interface, and a dial switch disposed on the circuit board. On the circuit board, the dial switch is disposed under the input interface. A part, corresponding to the dial switch, of the cabinet is provided with a dial switch opening. The dial switch passes through the cabinet through the dial switch opening. According to the utility model, the cabinet of the numerical control system is provided with the dial switch opening. An effective level-setting switch of the input port can be arranged under the condition that the numerical control system is not opened. Meanwhile, there is no need of welding an additional resistor at the outside, and each input port can be independently set. The switch is flexible in application, can be changed without professional knowledge of maintenance, and needs no wiring change or to weld an additional device.