Provided are a 3-terminal MIT switch which can easily control a discontinuous MIT jump and does not need a conventional gate insulating layer, a switching system including the 3-terminal MIT switch, and a method of controlling an MIT of the 3-terminal MIT switch. The 3-terminal MIT switch includes a 2-terminal MIT device, which generates discontinuous MIT in a transition voltage, an inlet electrode and an outlet electrode, which are respectively connected to each terminal of the 2-terminal MIT device, and a control electrode, which is connected to the inlet electrode and includes an external terminal separated from an external terminal of the inlet electrode, wherein an MIT of the 2-terminal MIT device is controlled according to a voltage or a current applied to the control electrode. The switching system includes the 3-terminal MIT switch, a voltage source connected to the inlet electrode, and a control source connected to the control electrode.