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..