Abstract: OBJECTIVE To investigate the etiology and risk factors of nosocomial infections after ureteroscopic holmium laser lithotripsy for ureteral calculi. METHODS A total of 101 cases of nosocomial infections after ureteroscopic holmium laser lithotripsy for ureteral calculi in our hospital from Jan. 2014 to Jan. 2016 were used as observation group, and 150 patients who received ureteroscopic holmium laser lithotripsy for the treatment of ureteral calculi without nosocomial infections at the same time were selected as control group. Specimens of infected patients were isolated, cultured and identified, drug sensitivity test was carried out, and risk factors of postoperative nosocomial infections of patients were analyzed. RESULTS A total of 159 strains of pathogenic bacteria were isolated and cultured from 101 patients, including 106 strains of gram-negative bacteria accounting for 66.67%, mainly Escherichia coli and Klebsiella pneumoniae, and 53 strains of gram-positive bacteria accounting for 33.33%,mainly Staphylococcus aureus and Enterococcus faecalis. The drug sensitivity test results suggested that the common pathogenic bacteria had high resistance to most commonly used antimicrobial agents, the overall degree of drug resistance was serious. The resistant rates of K.pneumoniae and E.coli to ampicillin and ciprofloxacin and norfloxacin were high, Pseudomonas aeruginosa was highly resistant to cefazolin and ampicillin, and was sensitive to piperacillin and imipenem. The main gram-positive bacteria had high resistant rate to erythromycin, penicillin and gentamicin, and were sensitive to vancomycin and teicoplanin. Age, operation time, diabetes mellitus and double J tube indwelling time were related factors of nosocomial infections after ureteroscopic holmium laser lithotripsy for ureteral calculi (P<0.05). CONCLUSION Nosocomial infections after ureteroscopic holmium laser lithotripsy for ureteral calculi are mainly gram-negative bacteria infection, and the overall degree of drug resistance is serious. The incidence of nosocomial infections should be reduced by targeted preventive measures, which has important significance to improve the clinical effect and medical quality.