Abstract: OBJECTIVE To explore the clinical significance of detection of plasma endotoxin (ET) in diagnosis of gram-positive bacteria, gram-negative bacteria, and viral infections before the use of antibiotics. METHODS A total of 124 fever patients who were treated in the hospital from Sep 2015 to Apr 2016 were enrolled in the study and divided into the bacterial group with 79 cases and the viral infection group with 45 cases; the bacterial group consisted of 45 cases of gram-negative bacteria infections and 34 cases of gram-positive bacteria infections.The serum endotoxin contents and white blood cell counts of the two groups of patients were determined. RESULTS The rank test and statistical analysis showed that the level of endotoxin of the patients with gram-negative bacteria infections was significantly higher than that of the patients with gram-positive bacteria infections and the patients with viral infections(P＜0.05).The white blood cell counts of the patients with gram-negative bacteria infection were increased with the level of endotoxin (r=0.354,P＜0.05). CONCLUSION The detection of plasma endotoxin level before the use of antibiotics may facilitate the preliminary identification of the species of bacteria and provide guidance for the reasonable clinical use of antibiotics.