Abstract: Sampling sites were established in a wastewater treatment plant (WWTP) with Anaerobic-Anoxic-Oxic (A²O) process to investigate the characteristics of odors and bioaerosols emission in the main sewage treatment unit. Results show that bacterial bioaerosols are dispersed in the main process sections, with detection quantity of 130-6 113 colony forming units/m³. More than 80% of bacterial bioaerosols are coarse particles larger than 2.1 μm in size. The microorganisms detected in the bioaerosols in the coarse grid, aeration tank and sludge dewatering room are mainly Pseudomonas sp., and other bacteria with higher abundances are Piscirickettsia sp., Staphylococcus sp. etc., of which Pseudomonas sp. and Stenotrophomonas sp. are potential pathogenic bacteria. Bioaerosol emissions vary seasonally, with concentrations significantly higher in autumn than in winter. The increase of temperature and relative humidity promotes the escape of bioaerosols, and wind speed is inversely correlated with the escape of bioaerosols. Suitable temperature and relative humidity contribute to the higher concentration of bioaerosols in each treatment section in September than in other months, and the risk of exposure to bioaerosols obtained by assessment is also high. The spraying of disinfectants reduces bacterial bioaerosols at the coarse grid and sludge dewatering room by 69.5% and 74.1%, respectively, which effectively controlls the emission of bioaerosols.