Modification method of in-situ Y zeolite

The invention relates to a modification method of in-situ Y zeolite. The method comprises the following steps of: (1) performing ammonia salt ion exchange on the in-situ Y zeolite serving as a raw material by using an aqueous solution of an ammonium salt to obtain ammonium type in-situ Y zeolite of which the Na2O weight content is less than 3.0 percent; (2) drying the ammonium type in-situ Y zeolite obtained in the step (1), and thermally treating under the protection of nitrogen; (3) selectively dealuminizing after thermal treatment; and (4) performing hydro-thermal treatment. Compared with the prior art, the invention has the advantage that: a product with appropriate performance can be obtained by adopting a simple treatment method. The modified in-situ Y zeolite can be taken as an acid component of a hydrocracking catalyst such as a medium oil hydrocracking catalyst with excellent medium oil selectivity and cracking activity.