In order to evaluate the clinical effect of low dose laser therapy on postoperative complications of mandibular impacted third molars, 22 randomized controlled clinical trials on complications of mandibular impacted third molars treated with low dose laser were obtained from CNKI, Wanfang, CBM, Pubmed, Embase and Cochrane library databases. The literature quality was evaluated by Cochrane Handbook 5.1.0 “bias risk assessment” tool. The meta analysis was conducted by Review Manager 5.3 software. The sources of heterogeneity were detected by sensitivity analysis and subgroup analysis, and publication bias was detected by funnel chart. The results of Meta analysis showed that low-dose laser therapy could significantly relieve the trismus, postoperative pain and swelling on the 2nd and 7th day after operation. The subgroup analysis was carried out according to different irradiation location and different output power. the results showed that combined intraoral and extraoral irradiation and intraoral irradiation could significantly relieve the trismus, swelling and pain 2 days after operation. Extraoral irradiation could not significantly relieve the trismus, swelling and pain 2 days after operation. Output power ≤ 100mW could significantly relieve trismus, swelling and pain 2 days after operation, output power 100~≤300 mW or ＞300~≤500 mW could significantly relieve postoperative pain, but could not significantly relieve the trismus and swelling 2 days after operation. Conclusion: low dose laser therapy can effectively relieve the pain, swelling and the trismus caused by impacted third molar extraction, and the irradiation mode and output power may affect the effect.