Abstract: Zeolite REUSL (ultra stable zeolite L modified by rare earth ions) with different contents of composite rare earth (La and Ce) was prepared by ionexchange, substituted for REUSY of 5% as an active additive component of catalytic cracking catalyst. The catalytic cracking performance of the catalysts with the REUSL zeolites was evaluated by microactivity testing (MAT) using diesel oil as a feedstock, and compared with the catalyst containing the zeolite USL modified by single rare earth element of La or Ce. The results show that the performance of the catalyst added zeolite USL modified by a proper amount of composite rare earth into the FCC catalyst is superior to zeolite USL modified by single rare earth element. The new catalyst can decrease the content of olefins in gasoline and increase octane number of gasoline. When composite rare earth content in zeolite REUSL is about 0.4%, compared with catalyst without zeolite REUSL, MAT index increases 3.6 units, the content of olefins decreases 1.57 units, research octane number(RON) increases 2.08 units, and catalytic product distributions are more excellent.