〔Abstract〕 Objective To explore the clinical effect of manual root planing technique in the treatment of severe chronic periodontitis (CP). Methods Sixty patients with severe CP treated in the Sixth Affiliated Hospital of Guangzhou Medical University from August 2022 to December 2022 were selected and divided into two groups by random number table method 30 patients in the observation group were treated with ultrasonic subgingival debridement + manual root planing technique, and 30 patients in the control group were treated with ultrasonic subgingival debridement. The clinical efficacy, periodontal indicators, and root surface sensitivity between the two groups were compared. Results There was no statistically significant difference in clinical treatment efficiency between the two groups (P > 0.05). At 1 month, 3 months, and 6 months after surgery, the bleeding index, probing depth, and clinical attachment loss of the two groups were lower than those before surgery, and the observation group had lower probing depth and clinical attachment loss than those in the control group, with statistical significance (P < 0.05). At 1 month, 3 months, and 6 months after surgery, there was no statistically significant difference in bleeding index between the two groups (P > 0.05). At 1 month, 3 months, and 6 months after surgery, the visual analogue scale (VAS) scores of the two groups were lower than those before surgery, and the VAS score of the observation group was higher than that of the control group at 1 month after surgery, with statistical significance (P < 0.05). At 3 and 6 months after surgery, there was no statistically significant difference in VAS scores between the two groups (P > 0.05). Conclusion Ultrasound subgingival debridement combined with manual root planing technique is effective in treating severe CP patients, but it is more effective in improving exploration depth and clinical attachment loss. Therefore, it is necessary to combine manual root planing to further improve periodontal status.