Abstract:Systematic research on formation mechanism of haze has been carried out in Chinese Academy of Sciences (CAS) by experiment simulation, field observation, and model simulation under the implemented the strategic priority research program of Category B "Formation Mechanism and Control Strategy of Haze in China". China's air pollution is formed by compounding a variety of emissions, showing a variety of sources, complex composition of pollutants, high concentrations, and different pollutants demonstrate the mutual influence and promote each other. According to the characteristics of haze formation, the basic principle of haze control at present stage should keep doing the emission reduction at the source, while focus on solving heavy pollution problems in the winter half, and further enhance the targeted control measures.