Objective To evaluate the effect of different gargling liquid on colony number in air during oral ultrasound scaling for patients with periodontitis. Methods Patients with mild(n=54), moderate(n=54), and severe chronic periodontitis(n=54) were selected, then patients with same degree of periodontitis were randomly divided into three groups, with 18 in each group. Before scaling, patients in each group of mild, moderate, and severe periodontitis were given honeysuckle liquid (gargle A), 3% hydrogen peroxide (gargle B), and normal saline (gargle C) respectively. Bacterial culture and identification of air specimens were conducted at 0 and 30 minutes after the beginning of ultrasonic scaling as well as 10, 20 minutes after the end of ultrasonic scaling. Results Variance analysis of three-factor factorial design data showed that degree of periodontitis, types of gargling liquid, and sampling time had interaction (F=2.666, P=0.002). Comparisons of air colonies:At the beginning of scaling, there was no significant difference in colony number of air around patients using different gargling liquid in mild, moderate and severe groups (all P>0.05). Among patients using the same gargling liquid at 30 minutes after the beginning of scaling, colony number of air was the lowest around patients with mild periodontitis and the highest around patients with severe periodontitis, colony numbers of air around patients with gargle A and B were lower than that of patients with gargle C. Comparison of each sampling points showed that colony number of air around the right side of patients' head was highest, differences were all statistically significant (all P<0.05). 20 minutes after the end of scaling, there was no significant difference in colony number among groups compared before scaling (all P>0.05). The main isolated strains in the air were Streptococcus viridans(32.53%), coagulase negative staphylococcus(24.56%), and filamentous fungi(18.48%). Conclusion There are variety of opportunistic pathogens in the air during oral ultrasound scaling, and the number of colonies is positively correlated with the degree of periodontitis. honeysuckle liquid has a good effect on reducing the number of air colonies during and after scaling.