Abstract: Objective：To explore the effect of microecologics combined with antibiotics on the prevention and treatment of severe pulmonary infection in ICU. Methods： A total of 80 patients with severe pulmonary infection who were admitted in ICU of our hospital from January 2017 to August 2017 were included in the study and divided into the observation group（n=40） and the control group（n=40） according to random number table method. The patients in the two groups were given antibiotics. On basis of routine treatment， the patients in the observation group were given microecologics. The changes of partial pressure of oxygen(PO2)， partial pressure of carbon dioxide (PCO2)， and white blood cell (WBC) count before and after treatment in the two groups were observed. The temperature recovery time， symptoms disappearance time， mechanical ventilation time， hospital stays， and clinical efficacy in the two groups were compared. Results： After treatment， PO2 in the two groups of patients was elevated compared with that before treatment， while PCO2 and WBC were reduced compared with those before treatment (P<0.05). After treatment， PO2 in the observation group was higher than that in the control group， while PCO2 and WBC were lower than those in the control group (P<0.05). The temperature recovery time， symptoms disappearance time， mechanical ventilation time， and hospital stays in the observation group were significantly lower than those in the control group (P<0.05). The treatment total effective rate in the observation group was higher than that in the control group (P<0.05). Conclusion： The microecologics combined with antibiotics can effectively alleviate the clinical symptoms in patients with severe pulmonary infection in ICU， and promote the rehabilitation， with a significant treatment advantage.