Abstract: The bifunctional catalysts for onestep DME synthesis were prepared by mixing JC207 catalyst and HZSM5 zeolites modified by MgO、CaO、ZnO,respectively. The evaluation of catalytic activity was conducted in a fixedbed reactor. Results show that Brostead acid site(strong acid sites) shifted to Lewis acid site (Weak acid sites) when the proper basic oxide was used to modify zeolite. Weak and less strong acid sites on the HZSM5 zeolite were activitive sites for the formation of DME whereas strong acid sites for by products such as hydrocarbons. Consequently, the selectivity of CO2 and hydrocarbons decreased over modified HZSM5 zeolite, especially over the zeolite modified by CaO.