Abstract: β zeolite was modified by dealumination with organic acid, and the physicochemical properties of the samples were characterized by XRD, BET, and NH3-TPD，27Al MASNMR，FTIR. Ethyl cyclohexane was used as a model compound to investigate the effect of modification on the performance of β zeolite for cycloparaffin ring-opening reaction. The results show that with increase of the dealumination degree, the crystallinity, specific surface area and acidic amount of the dealuminated β zeolites rise first and then decrease. The conversion，propylene yield and selectivity show the same trend. But little change of ethylene yield is observed. ECH ring-opening reaction reaches the optimal extent at 41.7% dealumination.