Objective：To analyze the efficacy and safety of flexible ureteroscopy with holmium laser（FURS） without a pre-existing ureteral stent for renal calculi. Methods：Clinical data of 716 patients who underwent FURS from July 2017 to December 2017 at this hospital were analyzed retrospectively. There were 377 patients without pre-existing ureteral stent and 339 patients with pre-existing ureteral stent. The overall the success rate of ureteral access sheath placement，operation time，overall hospital stay，stone free rate （SFR） and overall complication rate were compared between the two groups. Results：There was no significant difference between two groups in the preoperative stone size，stone location and SFR（94.1% vs. 93.7%）（P>0.05）. But there were significant differences be－tween two groups in the success rate of ureteral access sheath placement（90.2% vs.100.0%）（P<0.05）. No serious complication occurred in two groups. Conclusion：It is safe and effective for the FURS without pre-existing ureteral stent. Compared with the pre-existing group，there was no significant difference in the results. The success rate of FURS without pre-existing ureteral stent depends on the success of the sheath implantation and is related to the stricture or distortion of ureter，as well as the surgeon’s experience.