Used ultra-fine silicon oxide as carrier, the catalyst was prepared with the ZSM-5 molecular sieve with high n (SiO2)/n (Al2O3) ratio as active component for the catalytic cracking of C4 alkenes to propylene and ethylene. The precursors of CaO and La2O3 were used to adjust the acidic property of the catalyst. The catalyst was pretreated at 800with protection by inert gas or at 600with water vapor for 24 hours. At 500°C, 0.1MPa, w(H2O)w(C4＝)=0.2, WHSV 3 h-1, the catalyst evaluation was processed under the continuous operation for 25 days and the stability of catalyst was proved. The activity of the catalyst was reduced after long time treatment at the 800 °C or 600 °C with water vapor. The catalysts were characterized by BET, NH3-TPD and Py-IR, the results showed that the catalytic activity of the catalyst concerns with the quantity of the B acid.