In order to investigate the clinical and microbiological characteristics of patients with complicated intra-abdominal infections(cIAIs)in intensive care unit(ICU),the clinical data of 612 cIAIs patients from January 2016 to December 2018 were retrospectively collected.Clinical characteristics,distribution of pathogens and drug resistance were statistically analyzed.It was found that patients with community-acquired intra-abdominal infections(CA-IAIs)made up a majority of cIAIs patients.The positive rate of abdominal drainage fluid culture was 55.56％.Gram-negative bacteria accounted for the majority,the most commonly isolated bacteria of which were Escherichia coli(20.96％),Klebsiella pneumoniae(10.20％)and Pseudomonas aeruginosa(5.57％).The most commonly isolated gram-positive bacteria were Enterococcus(16.88％)and Methicillin-resistant staphylococcus aureus(MRSA,3.90％).Enterobacter isolates showed high resistance rate to most cephalosporins and low resistance rate to piperacillin/tazobactam and carbapenems.Extended spectrum beta-lactamase(ESBL)screen positive isolates from CA-IAIs patients showed an increasing trend in past three years.Enterococcus and MRSA showed high resistance rate to clindamycin,quinolone,erythromycin and tetracycline,while they showed high sensitivity rate to linezolid,tegacycline,teicoplanin and vancomycin.Our results indicate that isolated bacteria from abdominal drainage fluid show high resistance rates to commonly used antibiotics in ICU patients with cIAIs.The curative effects on diseases should be monitored continuously when antibiotics are used.Meanwhile,we should always keep eyes on drug-resistant bacteria,especially when the treatment efficacy is not good.