To investigate the feasibility of cationic antimicrobial peptide cathelicidin-PY(PY) therapy through a mouse model of acute liver failure.The ability of different concentrations of antimicrobial peptide PY to neutralize endotoxin / lipopolysaccharide (LPS) in vitro was detected by Limulus Amebocyte Lysate (LAL) assay. Cell counting kit-8 (CCK-8) was used to detect the toxic effect of different concentrations of antimicrobial peptide PY on mouse monocyte macrophages (RAW264.7). An in vitro hemolysis experiment was used to evaluate the activity of antimicrobial peptide PY on healthy human erythrocytes. D-galactosamine combined with LPS- induced mouse model of acute liver failure was constructed. The antimicrobial peptide PY effect on survival rate of mouse model was observed. HE staining was used to observe the pathological changes of liver tissue. Immunohistochemistry and Western blotting were used to detect the expression of apoptosis-associated protein caspase-3. Intra-group comparisons were performed using t-test and analysis of variance.(2) test was used for the comparison of rates.An in vitro experiment showed that the endotoxin neutralization rate was higher at very low dose (0.01 μmol/L), and exceeded 70% at medium-dose (10-40 μmol/L), and the difference between groups with different concentration was statistically significant (= 569.22,< 0.05). Medium-dose antimicrobial peptide PY had strong endotoxin neutralizing effect, low cytotoxicity and hemolytic activity. Moreover, in vivo experiments showed that the degree of liver injury and survival rate of mouse model was significantly improved with the medium-dose of antimicrobial peptide PY. Immunohistochemistry results showed that the expression of caspase-3 in the liver tissue was significantly depleted in the medium-dose group than that of the liver failure group, and the results were consistent with protein immunoblotting testing.Antimicrobial peptide PY possesses a strong ability to neutralize endotoxin and few toxic side effects. A specific dose of antimicrobial peptide PY can attenuate hepatocyte apoptosis and significantly improve the survival rate of animal model, and thus provides a new idea for the liver failure treatment.