ObjectiveTo analyze the clinical expression significance of IL－17 in peripheral blood of patients with severe pneumonia.MethodsA total of 100 patients diagnosed as severe pneumonia from January 2015 to January 2016 were selected in our hospital.According to the acute physiology and chronic health evaluationⅡ (APACHEⅡ),they were divided into group A(APACHEⅡ score＞20 points)and group B(APACHEⅡ score≤20 points).Another group of 100 healthy people after physical examinations from the same period was chosen as control group.The body temperature(T),white blood cell(WBC)count,procalcitonin(PCT),blood lactic acid(Lac),and interleukin－17(IL－17)were all tested among three groups.The difference of these outcomes were compared.ResultsT,WBC,PCT,Lac,and IL－17 in group A and B were much higher than those in the control group with statistical differences(P＜0.05).Between group A and B,there was no statistical differences was displayed in T,WBC,PCT,or Lac(P＞0.05),but with regard to IL－17,there was a statistical difference (P＜0.05).ConclusionIL－17 in patients with severe pneumonia is significantly higher than that in the healthy,and the level increases with the exacerbation of disease conditions,which indicates that increase of IL－17 level can reflect the condition of patients.