Objective To investigate the effect of dexamethasone addition in block anesthesia before surgery on postoperative quality of life after extraction of impacted mandibular wisdom teeth. Methods Using a random number table, 120 cases of patients were divided into experimental and control groups, each group contains 60 cases whose mandibular wis?dom tooth will be extracted. Before the surgery, the experimental group patients perform local block anesthetic injection with 3 mL out of 5 mL mixture of 2%lidocaine 4 mL+dexamethasone 1 mL (5 mg) to block nerve. The control group was given block anesthesia of inferior alveolar nerve with 3 mL of 2%lidocaine block anesthesia alone. Improved postoperative symp?toms severity scale (PoSSe) was used to evaluate patients’quality of life after tooth extraction comprehensively and quantita?tively by analysis and comparison of the two sets of scores. Results The experimental group’s PoSSe scores were 18.059 1 ± 13.210 9, which was lower compared with control group (27.819 3 ± 15.716 9). In experimental group, diet, language, swelling, pain and daily points were lower than the control group (P<0.05). Conclusion Topical application of dexamethasone in mandibular wisdom tooth extraction reduces postoperative adverse reactions in a certain degree and im?prove postoperative quality of life.