Two kinds of HZSM-5 zeolite (SiO2/Al2O3 = 50,300) were introduced into the STD (syngas-to-DME) reaction and the double-function catalysts containing CuO/ZnO/Al2O3 and HZSM-5 were investigated by activity evaluation and NH3-TPD. It was found that the acidity of HZSM-5 played a critical role in the performance of STD catalyst, and an appropriate acidic amount was required to obtain the best activity of STD catalyst; more and less acidic amount were both unfavorable for DME yield.