Sepsis is characterized by an innate immune response and the following immune dysfunction which can increase the emergence of secondary infections. Ethyl pyruvate (EP) has multiple immunoregulation functions in several serious illnesses, such as burn injury, severe sepsis and acute respiratory syndrome. However, little data was shown the effect of EP administration on immunosuppression post-CLP and the following secondary infection. The cecal ligation and puncture (CLP) followed by the induction of Pseudomonas aeruginosa (PA) was used as a clinically relevant two-hit model of sepsis. We assessed the survival rate, lung damage and lung bacterial clearance in vehicle or EP treatment group to demonstrate the lung response to Pseudomonas aeruginosa of septic mice. Then cytokines including lung IL-6, IL-1β, IL-10 and plasma HMGB1, apoptosis of splenic immune cells and Foxp3 level on regulatory T cells (Tregs) were studied to demonstrate the mechanisms of EP administration on two-hit mice. We found that the susceptibility of septic mice to Secondary Pseudomonas aeruginosa pneumonia could be down-regulated by ethyl pyruvate treatment and the protective effects of EP may via decreasing lung IL-10 and plasma HMGB1 expression, inhibiting the function of Tregs and relieving the apoptosis of splenic immune cells. The “immune paralysis” post-sepsis still remains a rigorous challenge for curing sepsis, our study may aid in the development of new therapeutic strategies to this problem.