Abstract: Water-chlorine balance of the system is very important for reforming catalyst to maintain good performance. The changes of physical-chemical properties and catalytic performance of CCR catalyst during commercial operation were studied. The deactivation of catalyst by water-chlorine imbalance and reactivation of said catalyst were investigated. Results show that the long-term imbalance of water-chlorine during operation leads to the decrease of chlorine content in catalyst, resulting in the severe agglomeration of Pt particles which reduce the activity and selectivity of catalyst significantly. The test results of a reforming catalyst collected from a CCR unit after running 1 967 d show that the maximum diameter of its Pt particle reaches 90 nm, as compared with fresh catalyst, its aromatics content in C5+ product is 12.89 percentage point lower, aromatics yield drops 10.59 percentage point and coke yield increases 0.77 percentage point. However, the redispersion of large Pt agglomerate is rather difficult under conventional oxychlorination and reduction conditions, especially under the operation conditions of CCR unit.