Abstract: This paper described the influence of Si addition in different ways on the performance of reforming catalysts. Introduction of Si-containing molecular sieve in catalysts increases the cracking activity and coking rate, and lowers the selectivity. The experiment find that the addition of Si in carrier preparation leads to the reduction of specific surface area and selectivity of the catalysts and higher coking rate and that after contaminated by Si during reforming reaction, the Cl-keeping capacity becomes poor and the catalyst activity is dropped as well. Si poisoning are irreversible and catalyst activity cannot be recovered through conventional regeneration method.