Abstract: A disordered mesoporous silica-alumina material (JSA) with pseudo-boehmite structures was successfully prepared through co-gel and aging process. It was studied in detail by XRD，BET，MPM，SEM，TEM，FT-IR and NH3-TPD. The results reveal that the material possesses large surface areas and pore volumes, and the average pore diameter is in the range of 8~12 nm. This material is formed by many spherical particles aggregated together and its micrograph looks like uniform wrinkles. It has both Lewis acid and Br?nsted acid centers as well as relatively high total acid content. The material shows pretty high hydrothermal stabilities. The FCC catalysts prepared with JSA display much higher cracking activities in the conversion of heavy oil and excellent selectivity of coke, and the distribution of cracking products is improved.