To analyze the factors influencing the operative time of severely displaced supracondylar fractures of humerus in children. [Methods] A retrospective analysis was performed on severely displaced supracondylar fractures of humerus in children hospitalized in 4 tertiary hospitals in Wuxi and Suzhou from January 2018 to April 2023. According to the operation time, the patients were divided into two groups: the short group was 76 cases, and the long group was 78 cases. Age, sex, obesity, nerve injury, injured side, displacement direction, Baumann Angle, degree of fracture rotation, fracture fragments, length of injured limb recovered from closed reduction in emergency room, and preoperative waiting time were compared between the two groups. t test and Chi-square test were used to incorporate binary Logistic regression analysis for factors with P < 0.25 to analyze the risk factors affecting the operation time. [Results] There were no significant differences in age, sex, nerve injury, injured side, displacement direction, Baumann Angle, degree of fracture rotation, and preoperative waiting time between the two groups (P>0.05). There were statistically significant differences in the length of affected limb after obesity, fracture fragments and closed reduction in emergency room (P<0.05). Binary Logistic regression analysis showed that the length of the affected limb and obesity were the risk factors affecting the operation time. [Conclusion] Good reduction in the emergency room can reduce the operation time, and obese patients should get good reduction in the emergency room to shorten the operation time.