A series of ultrastable Y zeolite samples (FSY) with high Si/Al ratio were prepared. The acid site amount of FSY samples could be effectively adjusted by dealumination with (NH4)(2)SiF6 and hydrothermal treatment. Therefore, the FSY sample with a suitable amount of acid sites and definite acidity could be expected. After being modified by lanthanum, the LaFSY zeolite with more strong acid sites and less weak acid sites was obtained, and it showed a high activity and gave a low coke yield in resid fluid catalytic cracking (RFCC). After being aged in 100 % water vapor at 800 degrees C for 17 h, the catalyst with the LaFSY zeolite as the active component gave a total liquid yield of 88.9% and coke yield of 7.5% in the RFCC reaction of Daqing resid. Compared with another generally used industrial catalyst that gave a total liquid yield of 85.4% and coke yield of 9.0%, the LaFSY catalyst could be considered as a better catalyst for RFCC.