本文设计了一个基于STC89C51单片机的数字频率计。该频率计包括单片机模块、放大整形模块、分频模块及显示四个模块。输入正弦和矩形信号经高频晶体管放大后，利用74HC14可得到高频高精度方波信号；利用74HC390可进行高精度分频以达到高频信号测量，并利用单片机在1s闸门时间内对输入信号进行计时、计数以获取频率值，通过LCD1602液晶显示器将频率显示出来。经试验验证，正弦信号频率可达10Hz-32MHz，电压有效值最低65mV-1V，相对误差0.01 ；矩形波频率可达150Hz-2.2MHz，峰峰值电压66mV-1V，测量数据刷新时间0.1s。本设计结构简单、价格成本低、操作方便，适用于日常生活、科研生产等领域。-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.