In order to solve the problems of manual counting of paper quantity,which is laborious and low accuracy,this paper designs a paper quantity detection device with automatic calibration function by combining FDC2214 capacitance sensor module with the master control module STM32 single chip microcomputer,which can realize accurate measurement of paper quantity between polar plates.According to the change of capacitance,the paper quantity can be obtained by fitting it.Compared with other paper measuring equipment,the detection device has the advantages of simple operation,faster reaction speed and higher accuracy.In the calibration process,the idea of interval fitting and curve fitting is used to fit the collected capacitance value,so as to improve the measurement accuracy.In the test mode,the paper test has fast reaction speed and high precision,and can realize the measurement of about 100 sheets of paper,and has wide application space in the quantity detection of paper.