Abstract: In this paper, pollution characteristics of PM_2.5 and PM₁₀ and their relationship with meteorological factors of Hohhot City in 2015 were analyzed using atmospheric environmental monitoring data and meteorological observation data in Hohhot City, and causes of thesevere fog and haze at the end of November in Hohhot City were analyzed preliminarily. The results showed that: (1)fine particulate matter pollution in HohhotCity was heavy, and the pollution of coarse particulate matter was relatively low.The concentrations ofPM_2.5 and PM₁₀ were highest in winter and lowest in summer, and the maximum monthly mean value of which in 2015 appeared in December.The trends of PM_2.5 and PM₁₀ concentration were basically the same in the whole year, andthe correlation coefficient of annual mean value was 0.711. (2)The correlation coefficient ofconcentrationof PM_2.5 and visibility,air pressure,relative humiditywere -0.887, 0.815,0.501,respectively. There is no significant correlation between concentration of PM_2.5and wind velocity and direction, precipitation, which may be related to the low annual mean wind velocity, notobviouschange of wind direction and precipitation phase. (3) One of the important reasons of persistent andabnormal strengthening of fog and haze of Hohhot City in November 2015 was related to the long time inversion layer over the Hohhot City, which was caused by increasing humidity (light to moderate drought in spring and summer and precipitation increased significantly in November),weak cold air force, low wind velocity and high temperature phenomenon. And winter heating is another important reason for the strengthening of pollutant concentration in November.