Objective To investigate the application of ultrasonic scaling combined with subgingival scaling in chronic periodontitis. Methods From March 2021 to January 2023, 90 patients with chronic periodontitis admitted to Changtong Community Health Service Center of Nanguan District in Changchun City were randomly divided into control group and observation group, with 45 patients in each group. The control group was treated with traditional subgingival scaling, and the observation group was treated with ultrasonic scaling combined with subgingival scaling. The clinical efficacy, periodontal index, pain degree and complications were compared between the two groups. Results The total effective rate of treatment in the observation group was 93.33%, which was higher than 73.33% in the control group, and the difference was statistically significant (P<0.05). The gingival index, periodontal pocket depth and gingival bleeding index of the observation group were lower than those of the control group, and the differences were statistically significant (P<0.05). The proportion of painless and mild pain in the observation group was higher than that in the control group, and the proportion of moderate and severe pain was lower than that in the control group, the differences were statistically significant (P<0.05). The incidence of complications in the observation group was 4.44%, which was lower than 17.78% in the control group, and the difference was statistically significant (P<0.05). Conclusion Ultrasonic scaling combined with subgingival scaling is effective in the treatment of chronic periodontitis, which can improve the periodontal index, reduce the pain degree of patients, and the incidence of complications is low.