Purpose: To evaluate the clinical outcomes of reconstruction using a collagen membrane, when a large perforation occurs during sinus lifting proceudure. Materials and Methods: This study included 18 patients who occurred a large perforation in the course of a sinus lifting at Seoul National University Bundang Hospital between September 2011 and March 2014. The cases have a variety of 5∼10 mm perforating size. We sealed the perforation using collagen membrane and bone graft was performed simultaneously. Thirteen patients had completed all treatments in the Seoul National University Bundang Hospital and the remaining 5 patients received the implant surgery from other dental clinics. We checked the information of implants, primary and secondary stability, types of complications, marginal bone loss, and resorptions of bone graft materials. Results: The average resorption was 2.46±1.17 mm 1 year after sinus bone graft, 3.99±1.96 mm 2 years after bone graft. The total average followup period of the patients was 38.13 months and the final average absorption was 4.10±2.03 mm. Intraoperative and postoperative complications included bleeding, hematoma, sinusitis, severe pain, peri-implantitis, and prosthesis dislodgement. Implant survival rate was 100% until the final follow-up period. The final alveolar bone resorption was 0.88±0.87 mm around the implant. Conclusions: The reconstruction using collagen membrane of large maxillary sinus perforation is very effective and successful treatment. When the maxillary sinus elevation and bone grafting are performed properly using a collagen membrane, there are many advantages about stability of bone graft materials for a long time and good retention and fuction of maintaining implants. (JOURNAL OF DENTAL IMPLANT RESEARCH 2017;36(1):1-5)