Objective? To investigate the relationship between body mass index (BMI) and common complications after extracorporeal shock wave lithotripsy (ESWL).Methods? A total of 213 patients who needed ESWL due to kidney stones in our hospital from January 2020 to November 2020 were enrolled. According to the guidelines for prevention and control of overweight and obesity among Chinese adults, the patients were divided into three group. Group A (58 cases, BMI<18.5? kg/m²), group B (120 cases, 18.5 kg/m²≤BMI<24 kg/m²) and group C (35 cases, BMI≥24 kg/m²). The serum creatinine and serum neutrophil gelatinase-associated lipocalin (NGAL) levels were compared between preoperative and postoperative day 1. The urinary system B-ltrasound was reexamined on postoperative day 1. The postoperative complications of ESWL in each group were scored and compared according to Clavien-Dindo classification.Results? The average lithotriptic energy of the 213 patients was (95.4±15.1) J, the average number of shocks was (1 230±310), and the average lithotriptic time was (21.6±10.2) min.Compared with 1 day before operation, there was significant difference in NGAL of the three groups 1 day after operation (P<0.05). Compared with group C, creatinine and NGAL in group A and B were significantly increased 1 day after ESWL operation, and the differences were statistically significant（all P<0.05）. Compared with group B, creatinine and NGAL in group A were significantly increased 1 day after ESWL operation, and the differences were statistically significant（all P<0.05）. In group A, 8 cases had Clavien Ⅰ complications, 4 cases had Clavien Ⅱ complications, and 1 case had Clavien Ⅲ complications. In group B,? 6 cases had Clavien Ⅰcomplications, 2 cases had Clavien Ⅱ complications. In group C, 2 cases had ClavienⅠcomplications, there were significant differences in complications among the three groups (P<0.05).Conclusions? BMI has a certain influence on postoperative complications of kidney stones after ESWL.The lower the BMI, the higher the risk of common postoperative complications.