Aim: The aim of this study was to evaluate the effectiveness of non-surgical periodontal treatment (NSPT) and its influential factors in a large Chinese population with chronic periodontitis. Methods: Periodontal examination data of 10,789 patients with at least one periodontal re-evaluation record were extracted from a hospital-based electronic periodontal charting record system. Probing depth (PD) and bleeding index (BI) reductions after NSPT and their influential factors were analysed by multilevel analysis. Results: Mean PD reductions at patient level and site level were 0.62 and 0.65 mm respectively. Mean reductions of percentage of tooth with BI > 1 and BI > 2 were 14.9% and 25.21%. Multilevel analysis demonstrated that PD and BI reductions were mainly influenced by baseline PD, baseline attachment loss (AL), baseline mobility, tooth type and frequency of periodontal maintenance (FPM). Besides, PD reduction was associated with baseline BI for all sites and was associated with gender and smoking status for sites with baseline PD ≥ 5 mm. Conclusion: The effectiveness of NSPT on patients with chronic periodontitis was proved in a large Chinese population. Outcomes of NSPT were mainly influenced by baseline PD, baseline AL, baseline mobility, tooth type and FPM.