ObjectiveTo evaluate the combined detection value of lactic acid(LA)  and Creactive protein (CRP)in the diagnosis of severe pneumonia.MethodsSerum LA and CRP levels in 40 patients who were diagnosed with ordinary pneumonia, 40 with severe pneumonia, and 30 healthy physical examination subjects (control group) were detected, diagnostic value in severe pneumonia was evaluated.ResultsSerum LA and CRP levels in patients with severe pneumonia were (9.90+1.30)mmol/L and (80.10+12.30)mg/L  respectively, which were higher than those in ordinary pneumonia (［4.90+0.50］mmol/L，［30.20+5.70］mg/L, respectively) and healthy control group (［1.20+0.10］mmol/L，［5.01+0.50］mg/L, respectively)，difference were both significant（both P<0.05）.  The sensitivity of separately detected LA and CRP were 75.0% and 60.0% respectively, specificity were 90.0% and 70.0% respectively， sensitivity and specificity of combined detection of LA and CRP were 90.0% and 85.7% respectively, sensitivity of combined detection was higher than that of separate detection(P<0.05); specificity of each group was not significantly different (P>0.05).ConclusionThe diagnostic value of serum LA level in severe pneumonia is better than that of CRP, combined detection of LA and CRP can improve the sensitivity, but will not decrease specificity.