ObjectiveTo investigate the distribution and change in antimicrobial resistance of pathogens causing bloodstream infection, so as to provide reference for rational antimicrobial use. MethodsThe isolation and antimicrobial resistance of major pathogens from blood culture specimens from a tertiary firstclass hospital in 2012-2015 were analyzed statistically. ResultsA total of 4 780 isolates were detected,  the top five species were Escherichia coli  (n=1 008, 21.09%), Klebsiella pneumoniae (n=624, 13.05%),  Acinetobacter baumannii ( n=452, 9.46%),  Staphylococcus aureus ( n=437, 9.14%), and  Pseudomonas aeruginosa (n=247, 5.17%). The percentage of gramnegative bacilli, grampositive cocci, fungi, and others were 62.05%, 29.31%,7.76%, and 0.88% respectively. The resistance rates of Klebsiella pneumoniae to ertapenem and imipenem increased from 4.50% in 2012 to 46.79% and 33.94% in 2015( both P＜0.01). The resistance rates of  Acinetobacter baumannii to cefepime, ceftazidime, tobramycin, gentamicin, and imipenem  were 86.50%, 80.56%,78.10%,79.87%, and 84.29% respectively；resistance rates to amikacin in 2012-2015 were 0,10.22%,39.85%, and 21.30% respectively（P＜0.01）；resistance rates to minocycline in four years were 0-7.52% ( P＜0.01). ConclusionThe main pathogens causing  bloodstream infection are gramnegative bacilli,  Acinetobacter baumannii is highly resistant to cephalosporins and carbapenems, resistance rates of Klebsiella pneumoniae to carbapenems increased rapidly. Broadspectrum antimicrobial agents must be used cautiously to reduce the selective pressure of antimicrobial agents.