The invention discloses a hydroisomerization catalyst and a preparation method thereof, and a method for producing base oil of lubricating oil from hydrocarbon oil or Fischer-Tropsch synthesis oil. The preparation method for the hydroisomerization catalyst comprises the following steps: (1) mixing amorphous silicon-aluminum, an alumina adhesive, nitric acid, an auxiliary agent and water so as to obtain a mixture and subjecting the mixture to mixing and kneading, extrusion molding, primary drying and secondary roasting so as to obtain a carrier precursor; (2) subjecting the carrier precursor to carrier modification in the presence of water vapor so as to obtain a modified carrier; (3) introducing a material containing an active component precursor to the modified carrier and carrying out secondary drying and secondary roasting so as to obtain a catalyst precursor; and (4) reducing the catalyst precursor in a hydrogen-containing atmosphere so as to obtain the hydroisomerization catalyst. The auxiliary agent used in the invention is nitrate and/or carbonate of alkali metals and/or alkaline earth metals. According to the invention, high yield of the isomerization product is realized; and the pour point of the product base oil of lubricating oil is reduced.