Objective To investigate the correlation of serum levels of lactate, procalcitonin (PCT), and C-reactive protein (CRP) with the score of acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) and sequential organ failure assessment (SOFA) score in the elderly patients with sepsis, and to analyze the prognostic values of these levels. Methods A total of 186 cases of senile sepsis in our hospital from January 2012 to December 2016 were selected and followed up for 28 d. According to their survival outcomes, they were divided into survival group (n=110) and death group (n=76). The serum levels of PCT, CRP and lactate in the 2 groups were detected, and the scores of APACHE Ⅱ and SOFA were recorded. Student’s t test, repeated measures analysis of variance, and Chi-square test or Fisher exact test were adopted for the data. Receiver-operating characteristic (ROC) curve analysis was employed to evaluate the prognostic values of the serum PCT, CRP and lactate levels in the septic elderly. Correlations of serum PCT, CRP and lactate levels with APACHE Ⅱ and SOFA scores were analyzed in the death group by Pearson linear correlation analysis.Results The serum levels of PCT, CRP and lactate in the first, third and seventh days were significantly higher in the death group than in the survival group (P<0.05). What’s more, the serum levels in the seventh day of the death group were obviously higher than those of the first and third days (P<0.05), but the levels in the seventh day of the survival group were notably lower than those of the first and third days (P<0.05). Logistic regression analysis found that serum levels of PCT, CRP and lactate, and SOFA score were independent factors for poor prognosis in the elderly patients with sepsis. The ROC curve showed that the best cut-off values of PCT_d3, CRP_d3 and lactate_d3 were 9.83 μg/L, 86.42 mg/L and 3.72 mmol/L in the evaluation of prognosis, with the sensitivity and specificity of 81.7% and 85.3%, 77.5% and 79.8%, and 86.3% and 76.2%, respectively. Correlation analysis indicated that the serum PCT_d3 level was positively correlated with APACHE Ⅱ and SOFA scores in the death group (r=0.703, P<0.001; r=0.802, P<0.001). Conclusion Serum PCT, CRP and lactate levels are closely related to the severity and prognosis of sepsis in elderly patients, and serum PCT level in the third day shows the greatest predictive value in the prognosis.