The invention discloses a catalyst for producing hydrocracking tail oil with low content of straight chain alkanes, and a preparation method thereof. The preparation method of the catalyst comprises the following steps: 1, uniformly mixing micro-porous alumina powder, modified USY molecular sieve and modified ZSM-48 molecular sieve powder, adding an acid solution, fully rolling the obtained mixture, molding the rolled mixture, drying the molded mixture, and roasting the dried mixture to obtain a catalyst carrier; and 2, impregnating the catalyst carrier obtained in step 1 in an impregnating solution containing active metal components, drying the impregnated carrier, and roasting the dried impregnated carrier to obtain the hydrocracking catalyst. The catalyst prepared through the method has the characteristics of high hydrogenation ring opening activity and good hydrogenation isomerism, and can be used for producing high-quality hydrocracking tail oil as lubricating oil base oil.