Objective To compare the anesthetic effect of modified local infiltration anesthesia with inferior alveolar nerve block anesthesia in the extraction of a high impacted third molar in the mandible. Methods Sixty⁃ seven patients undergoing bilateral extraction of medium to high mandibular obstructive teeth were anesthetized with modified local infiltration on one side and inferior alveolar nerve block on the other side. The pain sensation of injection（VAS self⁃assessment），lip and tongue numbness，operation time，anesthesia success rate，and intraop⁃ erative and postoperative pain were recorded and compared between them. Results The success rates of anesthe⁃ sia in the test and control groups were 93.8% and 93.7%，respectively（P = 0.964）. In the control group，3 and 2 patients did not experience intraoperative numbness of the tongue and lower lip，respectively，compared with 37 and 59 in the test group（P < 0.01）. The mean value of pain self⁃rating during anesthetic injection in the test group was significantly lower than in the control group（15.74 vs. 30.19，P < 0.01）. There were no statistical differences between the two groups in pain self⁃assessment values intraoperatively and at 2 hours，6 hours，1 day，2 days，3 days and 7 days postoperatively. Conclusion Modified local infiltration anesthesia for medium to high level man⁃ dibular blocked third molars can achieve similar anesthetic effect as block anesthesia does. It is superior to the block anesthesia，for it is easier to achieve minimal or no pain.