The invention relates to a preparation method of a linear-chain C5/C6 alkane catalyst prepared by sorbitol aqueous phase hydrogenation. The method comprises the following steps: (1) selecting activated carbon as a catalyst carrier, and drying at the temperature of 100-200 DEG C; (2) adding the dried activated carbon into an ammonium paramolybdate aqueous solution, and drying to obtain a catalyst carrier precursor containing molybdenum; (3) calcining the catalyst carrier precursor containing molybdenum in a muffle furnace to obtain a catalyst carrier containing molybdenum; (4) adding a ruthenium trichloride solution into the catalyst carrier for soaking, and drying to obtain a catalyst carrier precursor containing ruthenium and molybdenum; (5) calcining the catalyst carrier precursor containing ruthenium and molybdenum to obtain an initial catalyst; and (6) performing hydrogen gas reduction on the initial catalyst at the temperature of 250-400 DEG C for 4-8h to obtain the sorbitol aqueous phase hydrogenation catalyst. According to the method, a step soaking method is adopted to inhibit carbon-carbon bond breakage and selectively break carbon-oxygen bonds, so that the selectivity and the excitation capacity of sorbitol hydrodeoxygenation reaction can be improved.