Abstract: OBJECTIVE To observe the procalcitonin（PCT）, hypersensitivity protein C（CRP）, fibrinogen（FIB）, and antithrombin Ⅲ（AT-III） in patients with severe sepsis bacterial infection, and analyze their clinical significance. METHODS A total of 100 patients with severe sepsis bacterial infection treated in Baogang Hospital of Inner Mongolia from Feb. 2017 to Feb. 2018 were selected as the research subjects, and were divided into 58 cases of severe sepsis group and 42 cases of septic shock group according to the severity of the disease. The prognosis of all the patients were observed. Serum inflammatory factors such as PCT and CRP, coagulation indicators such as FIB and AT-Ⅲ, and immune functions indicators including immunoglobulin G（IgG）, immunoglobulin A（IgA） and immunoglobulin M（IgM） in survived and death patients with severe sepsis and septic shock were observed, and the correlation between inflammatory factors and coagulation indicators such as FIB, AT-Ⅲ and immune function in patients with severe sepsis bacterial infection were analyzed. RESULTS The levels of PCT, CRP and IL-6 of patients in septic shock group were（6.85±0.89）ng/ml,（448.98±15.06）mg/dl, and（49.95±4.32）pg/ml, respectively, significantly higher than those of patients in severe sepsis group（P＜0.001）. The IgG, IgA, IgM, FIB and AT-Ⅲ of patients in septic shock group were（9.05±1.76）g/L,（2.30±1.11）g/L,（1.41±0.97）g/L,（2.23±0.48）g/L, and（152.35±5.41） mg/L, respectively, significantly lower than those of patients in the severe sepsis group（P＜0.001）. The serum PCT, CRP, and IL-6 of the death patients were（8.11±1.25）ng/ml,（485.76±10.98）mg/dl, and（55.12±4.28）pg/ml, respectively, significantly higher than those of the survival patients（P＜0.001）. The levels of IgG, IgA, IgM, FIB and AT-Ⅲ of the dead patients were（8.02±1.69）g/L,（2.15±0.78）g/L,（1.25±0.92）g/L,（2.14±0.65）g/L, and（138.94±4.82）mg/L, respectively, significantly lower than those of the survival patients（P＜0.001）. The PCT, CRP and IL-6 levels of patients in severe sepsis infection group were negatively correlated with IgG, IgA, IgM, FIB and AT-Ⅲ levels（P＜0.05）. CONCLUSIONS The PCT and CRP levels were higher in patients with severe septic bacterial infection, while FIB and AT-Ⅲ levels were lower, which were related to disease severity and prognosis of the patients.