Abstract: To investigate the distribution characteristics and influencing factors of Enterobacteriaceae loaded by size-segregated bioaerosols from wastewater treatment plants (WWTPs), size-segregated bioaerosols in different seasons were collected within and around a WWTP in Jiangsu Province, and the concentration of the loaded Enterobacteriaceae was then analyzed. For the Enterobacteriaceae in overall bioaerosols and corresponding respiratory fragments, winter was the dominant emission season, and the sludge dewatering room was the main emission unit. Significant difference of Enterobacteriaceae loaded on size-segregated bioaerosols from WWTPs was found among different seasons or treatment units. Compared to upwind, the WWTP and downwind were characterized with higher enrichment of Enterobacteriaceae in overall bioaerosols and corresponding respiratory fragments. The size distribution of Enterobacteriaceae loaded by bioaerosols was significantly different between the WWTP and upwind, with a dissimilarity of 64.32%; that between the WWTP and downwind were not significantly different, and the dissimilarity decreased to 32.17%. The relative humidity, temperature, wind speed, and solar radiation, all had significant effects on the Enterobacteriaceae loaded by size-segregated bioaerosols (P < 0.05); among them, the relative humidity was the predominant factor. This study can provide a theoretical basis for the risk assessment and control of bioaerosol pollution in WWTPs.