Abstract: OBJECTIVE To explore the effects of the inflammatory indexes such as procalcitonin (PCT), C-reactive protein (CRP) and white blood cell (WBC )counts on evaluation of severity of sepsis in intensive care unit (ICU) patients and prediction of treatment outcomes. METHODS A total of 174 patients who were transfer to ICU for treatment from Jan 2016 to Jan 2017 were recruited as the stud objects and divided into the non-sepsis group with 96 cases and the sepsis group with 78 cases according to the criteria for diagnosis of sepsis. The levels of PCT, CRP, peripheral blood WBC counts, interleukin-6 (IL-6) and lactic acid (Lac) of the patients were detected on the first day of transfer to ICU. The Acute Physiology and Chronic Health Evaluation (APCHE II score and Sequential Organ Failure Assessment (SOFA) score of the patients were recorded. RESULTS The levels of PCT, CRP, WBC, IL-6 and Lac of the sepsis group were significantly higher than those of the non-sepsis group (P<0.05). According to the severity of sepsis, there were significant differences in the PCT, CRP, WBC, APCHEⅡ score and SOFA score among the general sepsis group, the severe sepsis group and the MODS group (P<0.05). The ROC curve indicated that the severity of infection was positively correlated with the PCT, Lac, APCHEⅡ score and SOFA score, and the specificity of the PCT was the highest in the early diagnosis of sepsis, higher than that of other indexes. CONCLUSION The severity of infection shows significant association with the inflammatory indexes, the serum PCT shows favorable value in diagnosis and prediction of systemic inflammatory response syndrome induced by the infection, the higher the level of the serum PCT is, the severer the infection; it is necessary for the hospital to control the illness condition based on the serum PCT level.