Abstract: OBJECTIVE To observe the clinical effect of combined detection of procalcitonin (PCT) and C-reactive protein (CRP) on sepsis patients with gram-negative bacilli bloodstream infections so as to improve the clinical significance in diagnosis of the gram-negative bacteria infections. METHODS A total of 80 sepsis patients with gram-negative bacilli bloodstream infections who were treated in the hospital from Apr 2013 to Apr 2015 were assigned as the experimental group, meanwhile, 80 patients with other local infections were set as the control group. The clinical indicators were observed and compared between the two groups of patients, and the statistical analysis of data was performed with the use of SPSS 16.0 software. RESULTS The levels of PCT and CRP were higher in the experimental group than in the control group; the positive rates of PCT and CRP were higher in the experimental group than in the control group, and there was significant difference (P<0.05). The specificity of the combined detection of CRP and PCT was 91.82%, the sensitivity 79.10%, the positive predictive value 90.42%, the Youden index 70.53%, the negative predictive value 81.29%. CONCLUSION The combined detection of CRP and PCT has high value in diagnosis of the sepsis patients with gram-negative bacilli bloodstream infections, and it can improve the effectiveness of diagnosis.