Aiming at the disability of receptor model in the source apportionment for secondary organic and inorganic aerosols in PM_2.5,a pollutant Inventory-based Chemical Mass Balance(I-CMB) model for source apportionment of PM_2.5 is established,and the recent actual pollution data in Beijing is put into the model.Results show that the coal is the largest source(accounting for about 28.06%) of PM_2.5 in Beijing,followed by the vehicle(19.73%),dust(17.88%),industry(16.50%),food(3.43%),and plants(3.40%).Compared to conventional CMB(Chemical Mass Balance),application of I-CMB in source apportionment requires less accurate source profile and is more resistant to interference,and the result is more balanced and detailed.The I-CMB model meets the demands of PM_2.5 reduction in China.