The capacitive level switch uses the probe (sensing electrode) and the container wall (grounding electrode) of the switch as the two plates of the capacitor. Due to the difference of dielectric constants of the air and the measured medium between the two plates, therefore when the level of the tested medium between the two plates of the capacitor changes, the capacitance value will also change. When the capacitance value changes to the set value of the switch, the switch signal is output for response control, achieving high and low material level detection and alarm.