purpose: To evaluate the efficacy and safety of flexible ureteroscopy and laser lithotripsy(FURSL) for treatment of the upper urinary tract calculi. Methods: We retrospectively analyzed 784 patients who underwent FURSL between January 2015 to October 2020 in our unit. The operative parameters, postoperative functional outcomes and complications were recorded respectively. Rusults: All patients underwent successful operation. The mean operative time was 46.9±15.8min. The average postoperative hospital stay was 1.2±1.1 days. The postoperative serum creatinine and hemoglobin were 76.2±10.2umol/L and 133.6±5.1g/L, which compared to preoperative, there were no sigificant statistical difference. Among 784 patients, 746 patients were followed up and 38 patients were lost. 700(93.8%) cases met the stone removal critetia and 46 cases(6.2%) did not meet the stone removal criteria for other treatments, such as extracorporeal shock wave lithotripsy, ureteroscopy and observed regularly. The stone free rate(SFR) is 92.5% after 1-3 months and SFR of middle and upper calyceal calculi was higher than that of lower calyceal calculi significantly. The most common complications were fever(58/784,7.4%),gross hematuria(540/784,68.88%) and lpsilateral low back pain(47/784,5.99). The incidence rate of serious complication was 1.28%(10/784), including 5 cases of septic shock and 5 cases of subcapsular hematoma, which were cured after active treatment. Conclusion: FURSL is a reliable treatment for small and medium calculi patients of upper urinary tract. The curative effect of stone removal is clear,the complications are few and the safety is high. However there are certain limitation to the efficacy in the treatment of large stone and lower calyceal calculi.