The aerosol optical depth (AOD) product of Himawari-8 satellite can be used to estimate PM_2.5 concentration near the earth surface with wide spatial coverage and high temporal resolution. Based on the three-dimensional variational assimilation system, the PM_2.5 data estimated by AOD are assimilated into the WRF-Chem atmospheric chemistry model. Then through the comparative analysis of control experiment and assimilation experiment, the improvement of PM_2.5 pollution simulation by assimilation of PM_2.5 data estimated by AOD is discussed. The results show that the assimilation of PM_2.5 data estimated by AOD has a significant effect on the improvement of the background field, resulting in the significant improvement of PM_2.5 pollution prediction. And in other hand, the improvement of PM_2.5 pollution from AOD variational assimilation is different in time and space. In addition, compared with the other methods using AOD observation operators directly to assimilate AOD, this method has the advantage of easy operation.