Methanol dehydration at vapor phase atmospheric pressure in fixed bed (2.54 cm inside diameter X 110 cm meter high) catalytic reactor was studied in this investigation. Three catalysts were used (Alumina, Ziolite 5A and resin) and moderate range of temperature (90-120 0C). Weight ratio of catalyst to molar flow rate (W/FA) from 27 to 81 (gcat.hr/gmol) was selected. Both Alumina and ziolite showed weak activity at this range of temperature while resin was better. Conversion of methanol to DME showed significant dependence on increasing temperature and flow rate (highest conversion was 8% at 120 0C and W/F=81 gcat. hr/gmol). Deactivation of resin with time was studied at optimum conditions, results showed no effect of time on both conversion and selectivity to produce DME. DME production selectivity was 100% at all operation circumstances. The nature of active sites of resin was studied by using selectivity poison procedure. Accordingly, acidic sites were mainly concerned with the reaction whereas Bronsted acidity has mainly contributed to the acidic sites.