A piezoelectric variable-frequency contact type liquid level switch belongs to the field of liquid level detection switches, and comprises a tube, wherein a probe support is arranged at one end of the tube, the piezoelectric variable-frequency contact type liquid level switch is characterized in that the probe support is fixedly provided with a piezoelectric ceramic sheet and a thermosensitive resistor which are respectively connected and arranged in a circuit board in the tube by leads, the circuit board is provided with a power circuit, an oscillating circuit, a frequency-voltage conversion circuit, an amplifying circuit, an isolating circuit and a driving circuit which are connected in sequence electrically, the oscillating circuit is connected with the piezoelectric ceramic sheet, and the thermosensitive resistor is arranged on the frequency-voltage conversion circuit. The thermosensitive resistor can also be connected to the amplifying circuit for temperature compensation. The circuit board is simple in structure, fewer for parts, low in material cost, and less in expending of working time; after one-time corresponding arrangement is conducted, the piezoelectric variable-frequency contact type liquid level switch has the advantages of being low in cost, maintenance-free, high in property, long in service life, good in universality, wide in application range and large in measurement range.