The invention discloses a cracking gasification catalyst composition, a preparation method thereof, and a cracking gasification method of petroleum hydrocarbons. The cracking gasification catalyst composition comprises the following raw material in percentage by weight: 1-50% of a mesopore active silicon, phosphorus and aluminum material, wherein in terms of weight of oxides, the anhydrous chemical expression of the active mesopore material is (0-0.2)Na2O.(50-86)Al2O3.(12-50)SiO2.(0.5-10)P2O5, the specific surface area is 200-600m<2>/g, the pore volume is 0.5-1.8mL/g, and the average pore diameter is 8-18nm. The cracking active components comprise 50-95 wt% of Y-type molecular sieve components and 5-50wt% of MFI structural molecular sieve components. The catalyst composition has good cracking activity and gasification convertibility when being used in a heavy oil catalytic cracking-gasification combined technology, and particularly, a high liquefied gas yield can be obtained.