COVID-19 has alerted us about the need to quantify the effect of different environmental factors on the concentration distribution of bioaerosols. An experimental investigation was carried out to evaluate the effect of environmental factors, including air temperature, relative humidity, airflow speed and ultraviolet (UV) radiation, on the potential dispersion risk of bioaerosols in an enclosed space by tracking the Serratia marcescens as the tiny organisms. Research results indicated that the concentration of bioaerosols is the highest at the indoor air temperature of 25°C among the tested conditions (20°C, 25°C, 30°C and 35°C). The particle size of bioaerosols can be influenced by temperature, resulting in changes in the amount of settling. Increasing relative humidity from 50% to 80% and airflow speed from 1.5 m/s to 2.2 m/s have a negative impact on the dispersion of bioaerosols as the amount of particle settlement increases accordingly. As for the UV radiation parameters, a better disinfection efficiency was achieved at a radiation distance of 40 cm in the tested range of 20–50 cm and a radiation exposure time of 30 min in the tested range of 10–50 min. This study delivered novel data for the concentration distribution of bioaerosol under different environmental factors for creating a safe indoor environment.