Catalytic cracking of vacuum gas oil on aluminas mixed with steam-treated zeolites (SY and SM) was investigated at 500℃ using a micro-activity tester. The catalysts containing SY and alumina prepared at pH 9. 5 showed a higher conversion and more fraction of gasoline and K+D (kerosene+diesel) in products than those containing SM and alumina prepared at pH 7.8. This could be explained by acidic properties and pore structure of catalyst. The distribution of produced benzene, toluene and xylene on the catalyst containing SY or SM was different due to the pore size of zeolites. The difference in hydrogen transfer rate over the catalysts containing SY or SM leads to a different composition of unsaturated and saturated products.