This paper presents an innovative dust removal technology, Cloud-Air-Purifying (CAP), which combines electro-acoustic ultrasonic nebulization with a cyclone dust collector. A humid environment is produced in the cyclone to imitate natural clouds in which the rain drops are formed. This facilitates the ultrafine particles in the environment to absorb moisture and agglomerate. Consequently, the ultrafine particles will significantly increase in size and thus be much more efficiently collected by the cyclone. Experimental results of the collection of two kinds of particles show that CAP significantly improves the collection efficiency of PM2.5 particles compared to traditional gas cyclones. Furthermore, numerical simulation is used to study the dynamics of the fine particles in CAP environment, which verifies the positive effect of particle growth on the collection efficiency. Finally, the successful industrial applications of CAP technology are demonstrated. This paper confirms CAP as a novel and effective method for controlling air pollution.