Based on piezoelectric resonant frequency method,a piezoelectric resonant PM2.5 monitoring system is designed with the modular design concept.The sampling unit,resonant unit,frequency test and display unit,control unit and other components of the system are designed,and the integration and performance evaluation of the system are carried out.For this system,the sampling scheme of inertial impact particle principle integrated with electrostatic precipitation is adopted to realize the effective sampling of PM2.5 particles and reduce the effect of the environmental factor on the piezoelectric crystal detection performance.Two identical quartz crystal oscillator circuits are used to construct a dual quartz crystal resonator,and the relationship between the piezoelectric resonant frequency and the piezoelectric wafer quality is established,and the mass concentration of PM2.5 is determined based on the change of the piezoelectric resonant frequency.The system test results show that the PM2.5 test data are close to the official standard data, and the trend of data changes is consistent.The PM2.5 monitoring system can reflect the change of PM2.5 mass concentration in the measured area and meet PM2.5 monitoring requirements.