Abstract: The PdMoP/γ-Al₂O₃ catalyst was prepraed through loading the Pd, Mo, and P elements on the γ-Al₂O₃ support by incipient impregnation method and characterized by XRD, NH₃-TPD, XPS, Py-FTIR, nitrogen physisorption and STEM-EDS. The catalytic performance of PdMoP/γ-Al₂O₃ in the hydrodeoxygenation of soybean oil methyl ester to alkane biodiesel was invetigqated and the operation conditions were optimized. The results show that a combination of Pd, Mo and P elements can effectively adjust the catalyst acidity; Mo can reduce strong acidity, whereads P can enhance weak acidity, leading to a decrease in the B/L ratio of weak acid sites and a slight increase in the B/L ratio of strong acid sites. The optimized hydrodeoxygenation conditions are 315 ℃, 1.5 MPa, WHSV=0.5 h^-1, and V(hydrogen)/V(esters)=1100; under such conditions, the conversion of soybean oil methyl esters reaches 98.4% and the C_15-18 alkane yield is 91.5%.