Objective To evaluate the clinical value of modular flexible ureteroscope combined with Holmium laser for treatment of upper urinary calculi. Methods A total of 33 patients with upper urinary tract calculi, including 22 males and 11 females, aging 20-86, were recruited in the present study. Fourteen patients were with upper ureteral calculi, 1 with ureteral and upper calyx calculi, 1 with ureteral and middle calyx calculi, 1 with ureteral and lower calyx calculi, 1 with upper calyx calculi, 2 with middle calyx calculi, 5 with lower calyx calculi, and 8 with pelvis calculi. Twenty-six patients had left calculi and 7 had right calculi; one patient had negative calculi. The diameter of the calculi ranged 0.6-2.3 cm. The patients were under general or spinal anaesthesia and at cutting stone position. After dilating the ureter, we inserted the guide wire under the vision of F8/9.8 rigid ureteroscope, then F12/14 flexible ureteral access sheath. Finally, holmium laser lithotripsy was performed by F8.0 “Polyscope” modular flexible ureteroscope. The power of the laser was 1.0 J and frequency was 10-20 Hz. F6 D-J tube was regularly input for 4 weeks post-operation, and Forley-urethral tube was input for 1 to 7 days. KUB was performed 1 day post-operation to detect the result of lithotropsy and the position of Double-J tube (in some patients, KUB was performed 2-4 weeks post-operation). If more than 6mm residual stone was detected, ESWL was performed.Results Lithotripsy was performed successfully in 27 patients (27/33); the operation time was 25-75 min (averagely 38 min); and the bleeding in the operation was less. Two patients had low fever post-operation; there were no ureteral perforation, high fever or septicaemia. The success rate of one-time lithotripsy was 82%. In the other 6 patients (6/33), 1 patient was transferred to ESWL due to polypi around the stone; 1 was transferred to PCNL due to ureter stricture,2 were transferred to ESWL due to small angle of lower calyx and pelvis, and 2 were transferred to URS due to ureter stricture.Conclusion F8 modular flexible ureteroscope is safe, convenient, and effective for lithotripsy of the upper tract calculi, especially for upper ureteral, pelvis, middle calyx, upper calyx stones.