Dimethyl ether is a clean and economical fuel alternative for petrodiesel. It can also be used as a substitute for chlorofluorocarbons and propellant sprays. As a chemical intermediate, it can be used to produce gasoline, ethylene, and other aromatic chemicals. In the present study, dehydration of methanol to dimethyl ether was investigated in an adiabatic fixed bed flow microreactor using the nanosize synthesized zeolite catalyst (H-ZSM-5) with hydrothermal crystallization method at different operating conditions. The structure of the synthesized zeolite catalyst was studied using X-ray diffraction, NH3-temperature programmed desorption, scanning electron microscopy, and Brunauer-Emmett-Teller techniques. The synthesized catalyst with silica to aluminum ratio of 67.7 showed high crystallinity and high surface area. The activity test also showed that the maximum yield of reaction was observed at a temperature range of 240 to 250 degrees C and weight hourly space velocity of 15 h(-1). At a temperature above 270 degrees C more by-products were produced.