The invention provides modified Y zeolite and a preparation method thereof. The modified Y zeolite contains 1-15 wt% of IVB family metal according to oxide and 0.1-10.0 wt% of phosphorus according to P. The ratio of the content of metal on the surface of the zeolite to the content of metal in the zeolite is not higher than 0.2. The preparation method of the modified Y zeolite includes the steps of processing Y zeolite with water content not exceeding 5 wt% through organic solvent and modified metallic compound, conducting calcinating, and then conducting processing through a phosphorous containing compound and acid. The modified Y zeolite has heat and hydrothermal stability not lower than that of the rare earth modified Y zeolite and has higher coke selectivity.