Objective To investigate the causes and treatment of recurrent laryngeal nerve （RLN） injury during the operation of thyroidectomy. Methods Clinical data of 48 patients that RLN were injured during thyroidectomy in and out of our hospital from Jun. 2003 to Mar. 2007 were reviewed. Results No patient died while operation and staying in hospital. There were 47 cases of unilateral RLN injury, 1 case of bilateral RLN injury; 21 cases （43.7%） were injured because of suture or scar adhesion, 13 cases （27.1%） were partly broken with formed scar, 14 cases （29.2%） were completely cut off; The locations of RLN injuries were closely adjacent to the crossing of the inferior thyroid artery and RLN in 13 cases （27.1%） and 35 cases （72.9%） were within 2 cm below the point of RLN entering into throat. The injured RLN were repaired surgically in 43 cases, among which 39 cases’ phonation and vocal cord movement were restored completely or had their vocal cord movement recovered partly; There were only 4 cases that the phonation and vocal cord movement were not recovered. Another 5 cases that did not take any repair did not recovered naturally. Conclusion The location of most RLN injuries caused by mechanical injury during thyroid surgery is closely adjacent to the entrance of RLN into throat. Early nerve exploratory operation should be performed once the RLN is injured, and the method of repair should be decided according to concrete conditions of injury．