Abstract: Objective To explore the value of plasma procalcitonin (PCT)detection in dif-ferentiation and judgment of severe pyemia.Methods 70 patients with pyemia were divided into general pyemia group (n =23),severe pyemia group (n =28)and pyemia shock group (n =19), and plasma PCT,lactic acid,c-reactive protein,the acute physiology and chronic health evaluationⅡ 24 hours (APACHE Ⅱ)and 1,2,3 days in hospital as well as serum PCT,lactic acid,c-reac-tive protein were detected and compared.Results Plasma PCT,lactic acid,CRP and APACHE Ⅱscore of pyemia shock patients were significantly higher than the general pyemia group (P <0.05). Serum PCT,CRP and APACHE Ⅱ score of pyemia shock patients were significantly higher than that of severe pyemia group (P <0.05).15 patients with pyemia died,55 patients survived.72 hours plasma PCT,lactic acid,CRP and APACHE Ⅱ score in death group were significantly higher than the survival group (P < 0.01).When pyemia patients were admitted to hospital,PCT were positively correlated with APACHE Ⅱ scores (r =0.528,P <0.01).Conclusion PCT is superior to the current clinical application of CRP inflammatory response parameters,and it can be used as an early identification of systemic infection,judgment of pyemia severity and prognosis judgment in-dex.