Abstract: The LCR parameter measuring instrument is used for measuring the parameters of inductance L, capacitance C and resistance R. The traditional LCR parameter measuring instrument has the disadvantages of complex circuit structure, high cost and being unfavorable for widespread application. A simple-structured, high-performing and low-cost LCR parameter measuring instrument has been designed. This LCR parameter measuring instrument mainly consists of an oscillator, a signal selection switch, a single-chip microcomputer data processing system and a display. By using different manifestations of inductance L in the capacitor three-point oscillator or capacitance C and resistance R in the NE555RC oscillator, different frequency square wave voltage signals are generated. This square wave voltage signal is selected by an electronic switch and sent to the single-chip microcomputer for sampling processing, from which the frequency value f of the square wave voltage signal is measured. Then, the frequency value f is substituted into the corresponding calculation formula to calculate the corresponding parameter value, and finally sent to the display to show the corresponding measured parameter value. The LCR parameter measuring instrument has the advantages of simple structure, low cost, wide measurement range and high measurement accuracy.