Two parent NaY zeolites with different framework silica to alumina ratios were mixed together, then modified by combining of ion-exchange and steaming treatment. The obtained zeolite USY was characterized by X-ray diffractometer (XRD), Nitrogen physisorption, 27Al solid state magic angle spining nuclear magnetic resonace (27Al MAS NMR), temperature-programmed desorption of ammonia (NH3-TPD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The relative crystallinity of the one-pot USY zeolite was 70%. The mesopore volume was 0.200 cm3 ·g-1 and mesopore size distribution was found to be present at about 10 nm. The obtained one-pot USY zeolite showed improved mesopore volume and higher acid amount compared with the USY prepared by the high silica to alumina ratio of the parent NaY zeolite. Compared with the USY zeolite prepared by the low silica to alumina ratio of the parent NaY zeolite, the one-pot USY showed higher crystallinity and acid amount. Compared with the mixture of two different USY zeolites, higher acid amount was observed for the one-pot USY. There is a balance between mesopore production and acidity preservation of the obtained USY zeolite. The results showed that catalyst with one-pot USY zeolite could improve VGO catalytic cracking, the yields of gasoline and diesel were 61.96wt%, and the yield of coke was 8.23wt%.