Ambient bioaerosols in PM2.5 and PM10 samples were measured in Huangshi City, Hubei Province of China, during the autumn and winter seasons from November 2017 to February 2018. Both bioaerosol number concentration and size distribution (0.37–16 μm) were obtained by direct fluorescent staining coupled with microscopic imaging. Bioaerosol number concentrations ranged from 0.05 to 3.4 # cm-3 for PM2.5 and from 0.17 to 5.7 # cm-3 for PM10, with averages of 0.90 # cm-3 and 1.9 # cm-3, respectively. Bioaerosol numbers were dominated by fine particles of 0.37–2.5 μm diameter, while the proportion of submicron particles was more pronounced than supermicron particles. Assuming unit densities and spherical shapes to estimate mass concentrations, bioaerosols constituted 2.4 ± 1.9% of PM2.5 and 4.8 ± 3.2% of PM10 mass measured by a nearby compliance monitor. Higher bioaeorsol concentrations were observed in winter than during autumn, and on polluted than on non-polluted days. Under heavily-polluted conditions, bioaerosols in PM2.5 and PM10 were enriched by 6 and 3.7 times, respectively, as compared to the levels on non-polluted days and contributed up to 15% of PM10 mass. Rainfall and snowfall appeared to lower the bioaerosol levels. As enhanced emission controls on combustion and dust sources decrease PM levels in China, bioaerosols will constitute a larger fraction of measured PM concentrations.