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This paper designed a microcontroller based STC89C51 digital frequency meter. The frequency meter includes a single-chip module, amplification shaping module, frequency module and display four modules. Input sine and rectangular signal after amplification of high-frequency transistors, high-frequency precision use 74HC14 available square wave signal the use 74HC390 accuracy can be divided in order to achieve a high-frequency signal measurement, and the use of SCM in 1s gate time of the input signal for a time, in order to obtain a frequency count value through LCD1602 LCD display the frequency display. The test verified the sinusoidal signal frequency up to 10Hz-32MHz, the minimum rms voltage 65mV-1V, the relative error of 0.01 rectangular wave frequencies up to 150Hz-2.2MHz, peak to peak voltage of 66mV-1V, measurement data refresh time 0.1s. The design of the structure is simple, low cost price, easy to operate, suitable for areas of daily life, scientific research and production.