Abstract: HYSPLIT4.9as a trajectory model and Global Data Assimilation System (GDAS) meteorological data were used to compute the backward air flow trajectories from December 2010to November 2011. This study focused on four seasons. Analysis of the effect of different seasons and trajectories on various pollutants based upon cluster analysis and corresponding pollutants concentration such as SO₂, NO_2and PM₁₀ was conducted. In addition, the potential contribution algorithm combined with weight factors (WPSCF) was utilized to study the spatial probability distribution of PM₁₀ and NO_2area sources for four seasons. The results showed the direction of the air flow in Shanghai was associated with temporal changes, Northwestern and southwestern winds were dominant in autumn, winter and spring. There would be a significant impact on Shanghai, when a trajectory passed through major anthropogenic emission areas. This phenomenon occurred in high ρ(PM₁₀), ρ(SO₂) and ρ(NO₂) values, which is 162,4and 53μg/m³.During summer, ρ(PM₁₀), ρ(SO₂) and ρ(NO₂) were relatively lower due to cleaner air from the ocean, which is 47,9and 36μg/m³. In seasons of autumn, winter and spring, Shanghai has a similar probability distribution characteristic as in those PM₁₀ and SO_2sources areas.High WPSCF values (0.2-0.4) were concentrated in the south of Jiangsu province. Furthermore, contribution from Inner Mongolia, Henan, and Anhui provinces could not be ignored since the study revealed that these regions are the potential sources of PM₁₀ and NO_2in Shanghai. In summer, WPSCF value outside Shanghai was almost lower than 0.1, which demonstrates the contribution from area outside of Shanghai is insignificant.