Objective：To compare the efficacy and safety of different doses of preoperative phloroglucinol in retrograde intrarenal surgery(RIRS). Methods：A total of 329 patients in this study were divided into two groups based on the preoperative use of different doses of phloroglucinol，177 cases in the treatment group[67 cases in the normal dose group(80~120 mg)and 110 cases in the high dose group(160~200 mg)]and 152 cases in the control group. Furthermore，all patients with successful UAS insertion were divided into two groups based on the preoperative use of different doses of phloroglucinol，170 cases were included into the treatment group [64 cases in the normal dose group(80~120 mg)and 106 cases in the high dose group(160~200 mg)]while 130 cases were included into the control group. The baseline information of patients，the success rate of UAS insertion，the stonE-free rate，complication rate，the frequencies of postoperative analgesic drugs，operation time，hospital stays and total drug side effects were collected and analyzed. Results：The success rate of UAS insertion in control and treatment group was 85.50% and 96.00%，which were significantly different (P ＜ 0.05). In the control group and treatment group of the successful UAS insertion，the first⁃stage stonE-free rates were 39.23% and 82.94% . Stone ⁃free rates in first month were 59.23% and 92.35%，the average frequencies of postoperative analgesic drugs were (5.51±1.43)times and(3.70±1.36)times，the average operative time were(103.79±39.37)minutes and(70.14±26.31)minutes，whichall were significantly different(P ＜ 0.05). In the normal dose group and high dose group of the successful UAS insertion，the first⁃stage stone ⁃ free rates were 70.31% and 90.57%，stone ⁃ free rates in first month were 85.94% and 96.23%，the average frequencies of postoperative analgesic drugs were(4.13±1.56)times and(3.44±1.17)times，the average operative time were(75.78±21.71)minutes and(66.74±28.29)minutes，the average hospital stays were(4.09±2.47)days and(3.04±1.75)days，which were also significantly different(P ＜ 0.05). Conclusion：Preoperative intravenous infusion of phloroglucinol is safe and effective for RIRS，improving the success rate of UAS insertion，the first⁃stage and onE-month stonE-free rate as well as reducing postoperative pain and operative time. In addition，higher doses of phloroglucinol are more effective than normal doses.