The invention discloses a catalyst for producing high-quality hydrocracked tail oil and a preparation method for the catalyst. The preparation method for the catalyst comprises the following steps: (1) preparing an organic-base aqueous solution with the concentration of 0.15mol/L to 0.80mol/L, adding USY molecular sieves into the solution, carrying out treatment for 0.5 to 3 hours at the temperature of 50 DEG C to 90 DEG C so as to prepare modified USY molecular sieves, then, adding fumed silica and modified ZSM-48 molecular sieve powder into the modified USY molecular sieves, carrying out thorough milling, then, carrying out shaping, and then, carrying out drying and roasting, so as to obtain a catalyst support; (2) dipping the catalyst support obtained in the step (1) with a dipping solution containing active metal components, and then, carrying out drying and roasting, thereby obtaining the hydrocracking catalyst. The prepared hydrocracked tail oil has the characteristics of low straight-chain paraffin content, high isohydrocarbon content and high viscosity index and can serve as high-quality lubricating-oil base oil.