Abstract: In order to investigate the pollution characteristics of particulate matter (PM), gas pollutants and carbonaceous aerosol under different air quality levels, PM (PM₁₀ and PM_2.5), gas pollutants (SO₂, NO₂, CO and O₃) and carbonaceous aerosol (OC, EC and TC) were measured by SHARP monitoring instrument, Thermo EMS system and Sunset online OC/EC analyzer instrument from November 28^th to December 28^th, 2013. Furthermore, combining with the meteorological data and back-trajectory model (HYSPLIT), the diurnal variations and sources of air pollutants were discussed in haze episodes. Results showed that the average concentrations of PM_2.5, PM₁₀, SO₂, CO, NO₂, O₃, OC, EC, POC and SOC were 167.90 μg/m³, 248.86 μg/m³, 77.79 μg/m³, 1.47 mg/m³, 97.16 μg/m³, 28.50 μg/m³, 27.09 μg/m³, 7.72 μg/m³, 7.50 μg/m³ and 19.59 μg/m³ during the haze episode in Jiaxing City, which were 3.00, 2.50, 1.29, 1.84, 1.50, 0.86, 2.59, 2.19, 2.13 and 2.82 times higher than the standard concentrations respectively, when the air quality index was good (51 < AQI < 100). The rainfall showed different scavenging effects on air pollutants, which had greater scavenging impacts on coarse particles and had weak impacts on O₃. High concentrations of PM were responsible for the reduced visibility. The proportions of fine particles in PM increased with the increase of air pollution levels. The PM_2.5/PM₁₀ ratio reached to 70.31% when the air quality index was seriously polluted (AQI> 300), 14.04% higher than that when the air quality index was good. With the exacerbation of air quality, the effects of boundary layer became weak to air pollutants. Gas pollutants showed different diurnal variations but the sources of OC and EC were gradually consistent, the concentrations of SOC showed features of accumulation-explosion-accumulation-explosion. With the increase of haze pollution, the proportion of SOC gradually increased but that of primary carbonaceous aerosol (EC and POC) gradually decreased.