In order to clarify the dynamic change of air bacteria and its influencing factors in different forest types in limestone hills and their influence factors, we screened out those with good bacteriostatic effect, four typical stands in Xuzhou limestone mountain area were selected as experimental materials, the seasonal and daily changes of bacterial content in stands were studied by natural sedimentation method, temperature and humidity, wind speed, PM_2.5 and air negative ion concentration were monitored synchronously, analysed the relationship between the content of air bacteria and environmental factors. The results showed that:(1) Bacterial content in spring > autumn > summer > winter, the daily variation regularity in other seasons was‘ high in morning and evening and low in noon’ while ‘high in noon and low in morning and evening’ in winter; (2) There were significant differences in air bacterial content among different stand types in the same season (P < 0.05). In general, Melia azedarach was the best in inhibiting bacteria; (3) The content of air bacteria had an extremely significant positive correlation with humidity and PM_2.5, and an extremely significant negative correlation with air negative ions. In conclusion, Melia azedarach had the best bacteriostatic effect. Humidity, PM_2.5 and negative ions were the main factors influencing the air bacterial content. This study can provide a scientific basis for the construction of urban health forest and the planning of ecotourism in the area.