〔Abstract〕 Objective To analyze the differences in the intensive care unit (ICU) bacterial spectrum among different ICU types and specimen types, so as to provide a reference for the control and treatment of clinical ICU infection. Methods In this study, the microbiological information of all patients admitted to ICU from 2001 to 2012 was extracted from the critical intensive care database (MIMIC– Ⅲ ), and the distribution of bacterial profiles of different specimen types and ICU types was compared. Results A total of 54119 cases of positive microbial culture were included in the study, with an infection rate of 51.91%. The samples were collected from sputum, urine, blood, swab, alveolar lavage fluid, tissue, catheter, feces, etc. More specimens were collected from the respiratory system than other systems. The overall bacterial spectrum distribution is more common in yeast, Staphylococcus aureus, coagulase-negative staphylococcus, Escherichia coli, enterococcus and so on. The bacterial spectrum of different samples showed different microbial results. Staphylococcus infection was the most common in blood culture, and yeast infection was the most common in urine, sputum or alveolar lavage. The flora of different ICU types were similar in distribution, with yeast, Staphylococcus aureus, coagulase-negative staphylococcus, Escherichia coli and enterococcus being more common. Attention should be paid to Candida albicans for the neonatal intensive care unit flora. Conclusion There are differences in the distribution of infection bacteria spectrum among different ICU types and specimen types. Rational utilization of the distribution of bacterial spectrum in ICU, understanding of specimen sources and differences of bacterial spectrum in ICU types, and timely use of targeted anti-infection therapy are conducive to clinical treatment and ICU infection control.