This study focused on the effect of alumina properties on the catalytic performance in the dehydration of methanol to synthesize dimethyl ether. The catalysts (gamma-Al2O3 and eta-Al2O3) were prepared from boehmite and bayerite, respectively, via calcination at various temperatures. With heat treatment, the properties of alumina have been changed significantly. Under identical reaction conditions, gamma-Al2O3 calcined at 500 C and eta-Al2O3 calcined at 500 degrees C showed the highest catalytic activity, because of high acid site density among the same types of alumina. Interestingly, eta-Al2O3 showed higher catalytic activity than gamma-Al2O3, although both catalysts possess comparable acidic properties. This means the structure type of alumina is crucial to determine catalytic performance in this reaction.