Objective To investigate the efficacy and safety of different preoperative indwelling time of double J tube in the treatment of upper urinary tract calculus by transurethral flexible ureteroscopic lithotripsy(FURL).Methods 135 patients with upper urinary tract calculus who underwent transurethral FURL treatment were selected and divided into group A(1 week retention),group B(2 weeks retention)and group C(1 month retention)with 45 cases each according to the time of indentation of double J tubes.The efficacy and safety of FURL treatment in three groups were compared.Results There were no significant differences in operation time,intraoperative blood loss,postoperative hospital stay,stone removal time,success rate of channel sheath implantation at one time and stone clearance rate at one month after operation among the three groups(P>0.05).The urinary tract infection,irritation sign of bladder and gross hematuria in group A were significantly lower than those of group B and group C(P<0.05).There were no significant differences in fever and ureteral wall injury among the three groups(P>0.05).Conclusion In the treatment of upper urinary tract calculus by tranurethral FURL,the double J tube can be implanted for 1 week before operation to achieve ideal surgical treatment effect and reduce the risk of surgical complications.