The present invention discloses a Na-Y molecular sieve and a method for preparing the Na-Y molecular sieve, an H-Y molecular sieve and a method for preparing the H-Y molecular sieve, a hydrocracking catalyst, and a hydrocracking method. The average grain diameter of the Na-Y molecular sieve is 2~5μm, and the sum of pore volumes of pores in 1-10nm diameter accounts for 70~90% of the total pore volume of the Na-Y molecular sieve. The H-Y molecular sieve obtained from the large-grain Na-Y molecular sieve can be used as an acidic component in the hydrocracking catalyst. When the hydrocracking catalyst containing the H-Y molecular sieve is applied in the hydrocracking reaction of heavy oils that contain macromolecules, it can provide better cracking activity and product selectivity in the hydrocracking reaction.

The present invention discloses a modified Y molecular sieve, a preparation method and a use of the modified Y molecular sieve, a supported catalyst, and a hydrocracking method. The silica-alumina mole ratio in the surface layer of the modified Y molecular sieve is 20~100:1, and the silica-alumina mole ratio in the body phase of the modified Y molecular sieve is 8~30:1. When a hydrocracking catalyst prepared from the modified Y molecular sieve is used for hydrocracking, the hydrocracking catalyst has higher reactivity and higher nitrogen tolerance. The hydrocracking catalyst prepared from the modified Y molecular sieve is suitable for use for increasing the yield of diesel oil, increasing the yield of chemical materials, and catalyzed hydrogenation conversion of diesel oil, etc..