In order to treat residual oil in conventional FCC units, various aspects of catalyst improvement must be considered, such as how to get effective bottoms crackbility, lower selectivity of dry gas/coke or higher metals tolerance. Because residual oil contains many kinds of metals (Ni, V, Na), Conrandson carbon residue and asphaltene or basic nitrogen compunds, there are a lot of problems in FCC operation. A new catalyst has been developed by means of modifying zeolite or matrix in our laboratory. The developed catalyst has a excellent bottoms crackbility, lower hydrogen / coke selectivity and higher metal tolerance. The features of the catalyst and the actual performance in our commercial units will be shown in this paper. The liquid product yield has been improved and the catalyst consumption has reduced. In order to treat residual oil in conventional FCC units, various aspects of catalyst improvement must be considered, such as how to get effective bottoms crackbility, lower selectivity of dry gas / coke or higher metals tolerance. Ni, V, Na), Conrandson carbon residue and asphaltene or basic nitrogen compunds, there are a lot of problems in FCC operation. A new catalyst has been developed by means of modifying zeolite or matrix in our laboratory. The developed catalyst has a excellent The features of the catalyst and the actual performance in our commercial units will be shown in this paper. The liquid product yield has been improved and the catalyst consumption has reduced.