The invention discloses a hydrocracking catalyst carrier and a preparation method thereof. The catalyst carrier comprises a modified Y molecular sieve, amorphous aluminium silicon and alumina, wherein, the preparation method of the Y molecular sieve is as follows: the Y molecular sieve which is treated by mixed water solution of aluminum salt and acid in a heating way is adopted. The performance of the modified Y molecular sieve is as follows: specific surface is 800m<2>/g to 900m<2>/g, total aperture volume is 0.40ml/g-0.50ml/g, relative crystallinity is 90%-130%, cell parameter is 2.434-2.440nm, aluminium silicon mol ratio is 20-100, infrared acid volume is 0.3-0.8mmol/g, the ratio of the acid B and acid L is above 7.0, sodium oxide content is less than or equal to 0.05wt%. The hydrocracking catalyst prepared by the carrier has the advantages of high catalytic activity, good target product selectivity and can produce heavy naphtha, aviation fuel and diesel fuel, and the like, with high yield and good quality.