The airborne particle measuring system has good timeliness, adaptability and stability in operation. Data of cloud droplets and precipitation particles monitored and recorded can be processed and displayed for real time. Structure and working principle of this system are introduced briefly. Theory of cloud droplets and precipitation particles detection in this system are described in detail, as well as technical characteristics of this system are analyzed. Potential errors in practical application are discussed, finally some notes and recommendations on the practical application as well as researches and developments of PMS systems are proposed.