Objective: To evaluate the influence of alveolar ridge preservation on delayed implant with different bone defects.Methods: 60 patients with one mandible posterior tooth extraction were enrolled in the study.Cone Beam Computed Tomography (CBCT) was used to measure alveolar ridge bone defect before tooth extraction (level A: 3 to 5mm and level B: above 5mm).After tooth extraction, the sockets were treated with alveolar ridge preservation procedure (trial group) or left to heal spontaneously (control group) randomly.The changes of alveolar ridge dimension from baseline to 6 months were evaluated by CBCT.All sockets were inserted suitable implants at 6 months, and the implant stability and osseointegration condition were evaluated in the next 12 months.