Abstract: In this study, the weather system in Tianjin area was classified, and the air mass tracks arriving at Tianjin were simulated using backward trajectory models and clustered according to different synoptic patterns. The long-distance transport paths of air masses arriving at Tianjin with different synoptic patterns were analyzed. It was found that the air masses arriving at Tianjin were mainly from the northwest and southeast. The occurrence frequency of different synoptic patterns and its impact on the concentration of PM₁₀ during heating season and non-heating season were studied respectively. It was found that the synoptic patterns were likely to be the significant factor influencing the ambient concentrations of PM₁₀ in Tianjin. Occurrence frequency of synoptic patterns advantageous to atmospheric diffusion in the heating season was 84.2%, 17.3% more than that in the non-heating season （66.9%）. Occurrence frequency of synoptic patterns disadvantageous to atmospheric diffusion in the heating season was 15.8%, 16.4% less than that in the non-heating season （32.2%）. Occurrence frequency of synoptic patterns advantageous to atmospheric diffusion in the heating season was more than that in the non-heating season, while the frequency of synoptic patterns disadvantageous to atmospheric diffusion was less than that in the non-heating season. This is an important reason that PM₁₀ concentrations in the heating season of 2008 were slightly lower than those in the non-heating season, although particulate matter source emissions increased in the heating season.