Objective To evaluate the effectiveness of periodontal endoscope as an adjuvant therapy for the non-surgical periodontal treatment of patients with severe and generalized periodontitis. Methods Patients (n=13) were divided into three groups: patients treated with conventional subgingival scaling and root planing (SRP) (n=7, 408 sites) (group A), SRP using periodontal endoscope (n=4, 188 sites) (group B) or SRP with periodontal endoscope 3 months after initial SRP (n=2, 142 sites) (group C). Two subgroups were divided into 2 subgroups according to PD at the baseline: 4<PD≤6 mm as subgroup 1 and PD>6 mm as subgroup 2. Probing depth (PD), attachment loss (AL), gingival recession (GR) and bleeding on probing (BOP) were recorded. Results The results of 3 months after treatment showed all PD, AL, and GR values in group A1 were less than those in group B1 (P<0.05), but no significant difference in BOP was found between the two groups. The decrease in PD, BOP in group B2 was more obvious than those in group A2 (P<0.000 1), and the GR values in group B2 were more than those in group A2 (P<0.000 1). But the improvement of AL showed no statistical difference between the two groups (P=0.296 8). In group C1, no significant difference in PD, AL, and GR was observed after endoscopy-assisted therapy, but it was more effective for BOP (P<0.000 1). In group C2, the improvement in PD and AL was significantly different from the improvement in SRP alone (P=0.000 5, P=0.000 2) and was accompanied by more GR (P=0.000 5). Conclusion In non-surgical treatment of severe and generalized periodontitis, SRP can achieve good therapeutic effect on sites with 4<PD≤6 mm. For sites with PD>6 mm, the application of periodontal endoscopy can increase the effect, reducing PD and GR, which may be an effective supplement to the current non-surgical periodontal treatment.