Objective To provide evidence for clinical practice by analyzing the factors associated with bloodstream infection in ICU patients through retrospective case-control study. Methods Using self-made data collection form, 133 cases of blood sample record from HIS system during May 2013 to December 2015 at Peking Union Medical College Hospital ICU ward were collected. In this study, 54 patients with positive blood culture results were allocated to the case group while 79 patients with negative results were in the control group. Baseline characteristics, which included sex, age and chronic diseases, were almost the same between both groups. Binary Logistic regression analysis was used to identify factors related to blood infection. Results During May 2013 to December 2015, there were 54 blood infectious cases, among which 19 cases with positive gram bacteria accounted for 35.2%(19/54), 57.4%(31/54) of gram-negative bacilli and 7.4%(4/54) of fungal infection. Logistic regression analysis revealed that blood filtration treatment (OR=7.691), pulmonary infection (OR=7.682), ICU (OR=1.115), Acute Physiology and Chronic Health Evaluation (APACHEⅡ) scores(OR=1.096), procalcitonin (OR=1.065) were risk factors of bloodstream infection for ICU patients, while albumin (OR=0.763) was a protective factor. Conclusions Blood filtration treatment, pulmonary infection, hospital length of stay, APACHEⅡand procalcitonin are factors associated with bloodstream infection in ICU patients. Clinical procedures in ICU should mainly focus on improvement of prevention awareness, strict aseptic technology, professional quality of nursing staff. Besides, guarantee of patients′nutrition, effective treatment of primary diseases, and shortened hospital length of stay are also important to reduce the infection and improve quality of life of these patients.