A gasification catalyst for heavy oil processing, and a preparation method and application thereof. The gasification catalyst contains alkali metal oxides, alkaline earth metal oxides (or not) and the balance of the magnesium enriched magnesium aluminate spinel. With the total weight of the gasification catalyst as a benchmark and in terms of oxides, alkali metal oxides and alkaline earth metal oxides account for 15-40 wt%; with the total weight of the magnesium enriched magnesium aluminate spinel as a benchmark, the magnesium enriched magnesium aluminate spinel contains 28-45 wt% of magnesium oxide and 55-72 wt% of alumina, magnesium and aluminum form spinel structure, and the content of free magnesium oxide is 5-20 wt%. The gasification catalyst can be mixed with any heavy oil contact cracking catalyst for usage, and the gasification catalyst accounts for 0.5-40 wt% of the total weight of the contact agent mixture in the heavy oil catalytic cracking-coke gasification integrated process. The contact agent loses little potassium in the use process and can reduce the gasification temperature of coke on the spent catalyst, so as to play the energy-saving effect, and realize the function of vanadium capture.