Based on the conventional meteorological data, PM_2.5 concentration, lidar data, tower data combined with wind profile data on 13~17 October 2015 in Beijing, Tianjin and Hebei, thermal and dynamic structure of heavy air pollution process have been researched. The results showed that the thermal conditions turn better during the day, vertical direction in the lower boundary layer changes from top-down motion into tilting motion, while southerly winds strengthened, pollution was transported enhanced, the main reasons for this spatial structure was that quasi east-west isotherm changed into the northwest-southeast direction after the thermal conditions strengthened and gravity wave caused by mountain heating excited amplitude increased during the day, resulted in air pollutants transmitted to Beijing at high-altitude appeared up and down transmission in the vertical direction, PM_2.5 concentration increased rapidly, there was vertical exchange under the condition of near ground southerly transports on November 16th, above transport and dispersion mechanism may explain the phenomenon, which mixing height increased with an increased PM_2.5 concentration in the daytime under the background of region heavy pollution.