Abstract: OBJECTIVE To investigate the causes of a clustering case with multidrug-resistant Acinetobacter baumannii (MDR-Ab) in neonatal intensive care unit (NICU), so as to provide references for clinical treatment. METHODS By combination of prospective and retrospective investigation, 2 cases of children patients who were infected with MDR-Ab bloodstream infection in May 2013 were performed epidemiological study. RESULTS Ab isolated from 2 children patients' blood were sensitive to gentamycin, tobramycin, ciprofloxacin, levofloxacin and sulfamethoxazole/trimethoprim. Both children patients were recovered after therapy. A total of 11 cases of environmental specimens were taken, and Ab were isolated from 2 specimens taken from the rest of nutrient admixture used by these 2 children patients, which had the same antimicrobial resistant pattern with their blood culture. CONCLUSION The clustering case of MDR-Ab bloodstream infection in NICU is related to the contamination of nutrient admixture.