Ion-induced nucleation is one of the most significant pathway of aerosol particle formation in the atmosphere. Air molecules are radiated by the cosmic ray to generate a mass of initial primary ions which will quickly react with common trace air constituents, such as H2 O, H2 SO4 , HNO3 , NH3 and organic species to form more stable ions, called as cluster ions. Processes for aerosol formation are the competition between growth and evaporation. When the critical nucleus forms, the formed small aerosol particle growth become spontaneous. This critical diameter can be calculated and predicted to be about 1.6 nm with mass number more than 5000 amu at standard atmospheric condition. However, there exist many controversies on ion-induced nucleation to what extent of influencing global climate and new particle nucleation. More observations, molding and laboratory studies should be carried out to explore the mechanism of ion-induced nucleation clearly.