Objective To investigate the safety and feasibility of one-stage flexible ureteroscopic lithotripsy without ureteral access sheath or ureteral stent in the treatment of upper ureteral calculi and renal calculi with a long diameter of ≤10 mm. Methods A total of 70 patients with upper ureteral calculi or renal calculi with a long diameter of ≤10 mm who were admitted to Guang’an Hospital，West China Hospital of Sichuan University，from January 2023 to June 2024 were enrolled and randomly divided into experimental group （without ureteral access sheath or ureteral stent） and control group （with ureteral access sheath and ureteral stent），with 35 patients in each group. The patients in the experimental group did not use a ureteral access sheath or a ureteral stent，while those in the control group used the ureteral access sheath and the ureteral stent. The two groups were compared in terms of preoperative data，intraoperative complications，stone clearance rate，length of hospital stay，hospital costs，and postoperative complications. Results There were no significant differences between the two groups in preoperative data such as age，body mass index，sex，previous history of stone surgery，affected side，maximum stone diameter，C-reactive protein，aggregation system separation，preoperative CT value of stones，and stone location. The experimental group had a significantly shorter time of operation than the control group［（44.94±52.60） minutes vs. （52.60±14.22） minutes，t=2.240，P=0.030］. There were no significant differences between the two groups in intraoperative data such as ureteral injury，intraoperative leukocyte changes，and intraoperative blood loss. The experimental group had significantly lower hospital costs than the control group［（8041.89±1287.57） yuan vs. （13 011.63±1 780.21） yuan，t=13.450，P=0.000］. There were no significant differences between the experimental group and the control group in the postoperative data such as the length of hospital stay，the recurrence of calculi on CT at 1 and 3 months after surgery，stone clearance rate，postoperative urinary tract irritation，postoperative ureteral injury，postoperative hematuria，and postoperative hydronephrosis（P>0.05）. Conclusion One-stage flexible ureteroscopic lithotripsy without ureteral access sheath or ureteral stent is safe and feasible in the treatment of upper ureteral calculi and renal calculi with a long diameter of ≤10 mm and can effectively reduce hospital costs and time of operation.