Abstract： Objective:To explore the causes of converting into thoracotomy during thoracoscopy for children with congenital pulmonary cystic disease and to discuss the measures of dealing with perioperative complications.Methods:Clinical data were retrospectively reviewed for 766 children with pulmonary cystic disease undergoing thoracoscopy from March 2012 to September 2020.There were 468 boys and 298 girls with a median age of 14 (1-188) months.The causes of converting into thoracotomy were analyzed.Results:All operations were completed successfully.Among them, 738 underwent thoracoscopy and 28 converted into thoracotomy with a conversion rate of 3.7%.The causes for conversion included indistinct exposure of lesions (10.7%, 3/28), indistinct exposure of vessels and trachea causing endoscopic difficulties (60.7%, 17/28), intraoperative complications (7.1%, 2/28), concurrent surgery required for other complicated diseases (7.1%, 2/28) and intolerance of artificial pneumothorax (14.3%, 4/28). And intraoperative complications included intraoperative hemorrhage (n=7, 0.9%), lymphatic leakage (n=1, 0.1%) and tracheal injury (n=2, 0.3%). During a postoperative follow-up period of (1-102) months, no serious complication, such as death, occurred.Conclusions:The causes for converting into thoracotomy are diverse.It should be based upon comprehensive analysis of patient status, operative skills and anesthetic levels.The occurrence of surgical complications is associated with disease severity, operative experiences, surgical routes and standardized procedures.