The influence of mischmetal addition on physicochemical properties of PtSnNa/ZSM-5 catalyst was studied by means of XRF,H2 chemisorption,XRD,TPR,NH3-TPD and TPO techniques.The results showed that the presence of mischmetal had an obvious impact on the catalytic performance of the PtSnNa/ZSM-5 catalyst.A suitable content of mischmetal not only could enhance the interactions between Pt species and the support,but also inhibit the formation of coke during the reaction,thus improving the catalytic activity and stability.In our experiments,when the content of mischmetal was 3m％,the catalyst exhibited best catalytic performance.However,the continuous addition of mischmetal could promote the reduction of Sn species to metallic tin,which was disadvantageous to the reaction.