Objective: To observe the long-term health condition of the single-tooth dental implant at the first molar site, and to evaluate the related factors affecting the peri-implant health. Methods: In this study, 82 patients who were treated in the Second Clinical Division, Peking University School and Hos-pital of Stomatology from January 2008 to December 2020 were enrolled. Peri-implant tissue conditions were assessed by clinical and radiographic examination. The peri-implant probing depth (PPD), modified sulcus bleeding index (mSBI), modified plaque index (mPLI) and papilla index (PI) were recorded for 278 implants. The X-ray analysis included the restoration emergence angle (REA), the clinical crown-implant ratio (cC/I), the horizontal tooth-implant distance (HTID), the contact point level (CPL) and the embrasure surface area (ESA), etc. Kruskal-Wallis rank sum test and generalized estimation equation were used for statistical analysis. Results: The average age of the patients was (40.2±9.5) years (19 to 84 years), with 33 males and 49 females. The follow-up time was (4.9±3.3) years (1 to 10 years). According to the diagnostic criteria in 2018, the prevalence of peri-implantitis in this study was 14.03% on the implant level and 21.95% on the patient level. The peri-implant health rate was 19.06% on the implant level and 18.29% on the patient level. The prevalence of peri-implant mucositis was 66.91% on the implant level and 59.75% on the patient level. At the baseline, there were statistically significant differences between the peri-implant health group and peri-implantitis group in PPD, distal HTID and mesial/distal CPL, cC/I (P < 0.05), while there was no statistically significant difference in mSBI, mPLI, PI, mesial HTID, mesial/distal REA and mesial/distal ESA between the two groups. Among the differences between follow-up and baseline, there were statistically significant dif-ferences between the two groups in PPD, mesial/distal HTID, mesial/distal CPL and mesial/distal ESA (P < 0.05). Generalized estimation equation showed that PPD, mesial/distal HTID, mesial CPL, and mesial ESA had significant positive correlations with the risk of peri-implantitis in the difference between baseline and follow-up. Conclusion: Based on the results of this study, the peri-implant health rate is still unsatisfied, and the PPD, HTID, CPL, ESA may be related to the long-term health of the implant.