为实现金属板厚度的实时检测以期及时修正避免误差积累，本文以STC89C52单片机为控制核心，研制基于差动式电容传感器的金属板厚度在线检测系统。该系统通过差动式变极距电容式传感器，实现金属板厚度信号的采集；进而用定时器产生矩形波，单片机在一定时间内计数，最后得出频率，计算出金属板厚度；为了达到随时观察的目的，在系统中辅以显示模块，便于在生产过程中出现特殊情况时，可以被用户发现并及时纠错。该系统能迅速的进行响应，以达到生产要求中的实时性，且成本较低，具有一定的应用价值。 In order to realize the real-time detection of metal plate thickness in order to correct it in time and avoid error accumulation, this paper develops an on-line metal plate thickness detection system based on differential capacitance sensor with STC89C52 single chip microcomputer as the control core. The system realizes the acquisition of metal plate thickness signal through differential variable pole distance capacitive sensor; then the rectangular wave is generated by the timer, and the single chip microcomputer counts in a certain time. Finally, the frequency is obtained and the thickness of the metal plate is calculated; in order to achieve the purpose of observation at any time, the display module is supplemented in the system, so that in case of special circumstances in the production process, it can be found by the user and corrected in time. The system can respond quickly to meet the real-time production requirements, and the cost is low, so it has a certain application value.