[Abstract] The crown-to-root ratio of natural teeth has important clinical significance for evaluating the long-term status of natural teeth. However, a large number of clinical studies and animal experiments have shown that the theory of natural crown-to-root ratio is not suitable for implant restorations. The traditional implant concept is to implant a longer implant to improve the success rate of implantation. However, with the wide application of short implants, the effect of crown-implant ratio ( C / I ) on the clinical complications of implant-supported single crown restorations has attracted the attention of clinicians and scholars. Based on the systematic review and analysis of domestic and foreign literatures in recent years, this paper deeply studies the effect of crown-implant ratio ( C / I ) on the clinical complications and success rate of implant-supported single crown restorations. The results showed that there was no clear correlation between C / I ratio and implant clinical complications and implant success rate, but too high C / I may increase the risk of implant biological and mechanical complications. Clinicians should develop reasonable individualized treatment methods when using short implants to avoid the risk of high C / I, so as to achieve long-term stability of implant-supported single crown restorations.