A modified zeolite beta having an anhydrous chemical formula, by weight % of the oxides, of (0-0.3)Na2O.(0.5-10)Al2O3.(1.3-10)P2O5.(0.7-15)MxOy.(70-97)SiO2, wherein M is one or more transition metal(s) selected from the group consisting of Fe, Co, Ni, Cu, Mn, Zn and Sn, x is the number of the atoms of said transition metal M, and y is a number that meets with the requirement of the oxidation state of said transition metal M, is disclosed. The modified zeolite beta can be used as an active component of a cracking catalyst or additive for catalytic cracking of petroleum hydrocarbons.