Abstract: The characteristics of air pollution in Changzhou City were analyzed by using the measurement data of PM_2.5, PM₁₀, SO₂, NO₂ and CO in winter from 2013 to 2015. Hourly 48-hour backward trajectories at ground (100 m) level were used to study the effect of clusters on various pollutants. The potential source contribution function combined with weight factors (WPSCF) was applied to identify the potential sources and estimate the source contributions for air pollutions in winter. The results showed that PM_2.5 was the primary pollutant in winter in Changzhou City. The number of days with PM_2.5 as the primary pollutant accounted for more than 90% days in winter. The highest frequency of air quality level were good and slight polluted. The contribution of PM_2.5 in winter accounted for 37.4% of PM_2.5 annual mean, one reason of which was the incomplete combustion of fuel. Two peak pattern in the diurnal variations of ρ(PM_2.5), ρ(PM₁₀), ρ(SO₂), ρ(NO₂) and ρ(CO) were observed. The first peak value appeared in the early morning rush hours while the second one appeared around late evening, while the later peak of ρ(NO₂) was obviously larger than that of the first peak, while ρ(SO₂) and ρ(CO) behaved the opposite. The ratios of CO/NO_x and SO₂/NO_x suggested that mobile sources were the major contributor to gaseous pollutants in Changzhou City and the point sources had important effects on air quality. The gradient variation of ρ(PM_2.5) concentration in 1 and 6 h can be used to identify the explosive growth of ρ(PM_2.5). The continental airflow from the northwest, west and southwest regions had significant impact on Changzhou City and the corresponding ρ(PM_2.5), ρ(PM₁₀), ρ(SO₂), ρ(NO₂) and ρ(CO) values as well as the probability of the corresponding polluted trajectories were higher than airflows from other direction. The east airflow usually moved slowly and the atmospheric diffusion conditions were poor, which could easily lead to pollution accumulation and high concentrations of ρ(PM_2.5), ρ(SO₂) and ρ(NO₂). High WPSCF values (>0.5) were focused in the downstream of the Yangtze River from Wuhu to Shanghai and the Hangzhou Bay area. The potential sources of PM_2.5, PM₁₀, SO₂, NO₂ and CO were quite different. The contribution of local sources on NO₂, SO₂ and CO was more pronounced than that of PM_2.5 and PM₁₀. The marine pollution source would be a significant impact on NO₂, SO₂ and CO in the coastal area. The study showed that the local air pollution was highly related with the local anthropogenic air pollutant emission in the Yangtze River Delta region but the contribution of long-distance transport could not be ignored.