Abstract: Objective To explore the risk factors and preventive measures of nosocomial infection in patients with ureteral calculi after flexible ureteroscopic lithotripsy. Methods A total of 97 patients with ureteral calculi who suffered from nosocomial infection after flexible ureteroscopic lithotripsy treated in our hospital from May 2015 to May 2017 were selected. Pathogenic bacteria were cultured from patients' clean urine, and the types and drug resistance rates of pathogens were analyzed, and the risk factors of nosocomial infection were analyzed. Results A total of 141 pathogenic bacteria were detected in 97 patients, of which 96 (68.09%) were gram-negative bacteria, 28.13% were Escherichia coli, 45 (31.91%) were Gram-positive bacteria and 42.22% were Enterococcus faecalis. The drug resistance of Escherichia coli to gentamicin was the highest and its sensitivity to imipenem was the highest. Enterococcus faecalis was the most resistant to penicillin and Enterococcus faecalis was the most sensitive to vancomycin and furantoin. Of 97 patients with nosocomial infection, 7 had iatrogenic infection, 45 had improper wound care, 32 had upper genitourinary tract infection and 13 had other causes. The incidence of postoperative bleeding, postoperative pain, residual stones and postoperative renal injury increased significantly (all P<0.05). Multivariate analysis showed that postoperative pain, postoperative hemorrhage, postoperative renal injury and residual calculi were independent risk factors for renal injury after ureteroscopic lithotripsy (all P<0.05). Conclusion Escherichia coli and enterococcus faecalis are the main pathogens of infection in patients with ureteral calculi after flexible ureteroscopic lithotripsy. The risk factors include postoperative pain, postoperative hemorrhage, postoperative kidney injury, residual calculi and so on.