Abstract: Objective: To provide a quantity index for alveolar ridge augmentation at mandibular posterior area. Methods: According to anthropometry,the height of different points of mandibular posterior area was measured on 109 adult mandibles. Results: The height between superior margin of mental forman and alveolar ridge crest,dentulous side （13.95±2.45）mm,edentulous side （8.77±2.75）mm,difference of mean value 5.18mm;mandibular body heigt at mental forman area,dentulous side （31.65±3.09）mm,edentulous side （24.67±3.88）mm,difference of mean value 6.98mm;mandibular body height at posterior area,dentulous side （29.15±2.91）mm,edentulous side （23.03±4.11）mm,difference of mean value 6.12mm. Conclusion: To measure mandibular height at premolar and molar area,the use of mental forman and the point 1.0cm behind mental forman as mark point presents advantages such as approaching simply,constant measuring location and high reliability.The mean loss of bone at mandibular posterior area is 5－7mm,which should be referrible for alveolar ridge augmentation.