Abstract: Fourteen days were selected in the autumn and winter respectively to monitor the vertical distribution of PM_2.5 mass concentration in the ground layer of the atmosphere in Beijing. Vertical profiles of PM_2.5 mass concentration were obtained. Combined with the meteorological data measured simultaneously, the impact of meteorological factors on the vertical distribution was analyzed, and finally vertical profile fitting equations of PM_2.5 mass concentration were got. It is demonstrated that the vertical distribution of PM_2.5 mass concentration logarithmically decreases with the increase of the altitude obviously in the autumn and winter. The wind velocity varies with the altitude logarithmically. When there exists temperature inversion, the atmosphere stratification is stable and restrains the turbulence in the vertical direction, PM_2.5 hourly mass concentrations in the vertical direction are in linearity with the wind speed, and thus PM_2.5 mass concentration varies logarithmically with the altitude significantly. Under non temperature inversion conditions, the probability of PM_2.5 hourly mas concentrations in the vertical direction being in linearity with the wind speed is small, and the logarithmic relationship between the mass concentration and the altitude is not significant.