Objective: To provide anatomic basis for the mandibular dental implant operation of the clinical oral surgery. Methods: 10 fresh mandibles, 18 adult mandibles with total teeth and 20 volunteers without agomphosis were selected and exposed the inferior alveolar neurovascular bundle, the mandibular canal and the dental root of mandibular posterior teeth, scanned in series by CT，and then its three-dimensional image were reconstructed. The relationship of the inferior alveolar nerve with the inferior alveolar vessels were observed, the dental root of mandibular posterior teeth to the superior wall of mandibular canal was measured with vernier caliper and three-dimensional reestablish working station respectively. Results: The mandibular canal was traveling through the bottom of alveolar fossa. Its lingual side was thick, the inferior alveolar vessels were laid above the inferior alveolar nerve in the mandibular canal. The distance was near from the distal root of mandibular molar to the mandibular canal than that of the mesial root. The distance from the dental root of first premolar, second premolar, first molar, second molar, third molar to the superior wall of mandibular canal were 8.36±2.34 mm, 8.42±2.42 mm, 7.36±2.21 mm, 7.52±2.18 mm, 3.22±1.40 mm, 3.36±1.85 mm, 2.96±1.54 mm, 2.84±1.55 mm, 3.64±1.72 mm and 3.88±1.76 mm in specimen and imaging separately. Conclusions: (1) The distance from the second molar to the mandibular canal was the nearest than that of the others, it was the second molar, first molar, third molar, second premolar and first premolar from the near to the far. (2) It is significant for choosing appropriate length of dental implantation, which avoid the injury for the inferior alveolar nerve.