Objective: To evaluate the clinical effect and masticatory efficiency of two early loaded Small Diameter Implants (SDI) retained mandibular overdentures., Methods: Eight mandibular edentulous patients received two SDIs insertion between mental foramina. The mandibular overdentures were connected with implants for early loading in the period of 2-4 weeks following implant insertion. The data of visual analogue scale (VAS) of denture satisfaction and masticatory ability were collected at baseline, two weeks, three months and six months following overdenture loading. Masticatory efficiency was evaluated before surgery and six months after overdenture loading., Results: Within the period of six months following overdenture loading, all the 16 implants remained stable. Compared with the baseline, the VAS data of denture satisfaction,stability, masticatory and poltophagy ability two weeks, three months and six months after overdenture loading were significantly improved with 30 degree (P<0.01), especially the masticatory and poltophagy ability of hard and crisp food. The value of masticatory efficiency improved considerably six months after overdenture loading (P<0.01)., Conclusion: Mandibular overdentures retained by two SDIs can significantly improve patients' denture satisfaction and masticatory efficiency, and provide more rational diet.