The invention relates to a method for preparing methyl acetate through adopting a sectional heat insulation fixed bed reactor. A dimethyl ether raw material is distributed to all catalyst beds in a split feeding manner, a reactor adopts the sectional heat insulation fixed bed reactor containing a plurality of catalyst beds, the fed first dimethyl ether flow is mixed with a carbon monoxide raw material, the obtained mixture enters a first catalyst bed and undergoes a reaction, the obtained reaction product and a next fed dimethyl ether flow are mixed and undergo heat removal, the obtained mixture enters a next catalyst bed until the last fed dimethyl ether flow and a reaction product of the prior catalyst bed, undergo heat removal and undergo a reaction is carried out in the last catalyst bed in order to obtain a final reaction product, cooling the reaction product, carrying out gas-liquid separation to obtain a gas phase and a liquid phase which is the methyl acetate, circulating a part of the gas phase, mixing the part of the gas phase with the carbon monoxide raw material to obtain a reaction raw material, and discharging the remaining part of the gas phase to the outside. The method has the advantages of high methyl acetate selectivity, high catalyst filling rate, greatly reduced circulating gas flow, and saving of the device investment and the circulation energy consumption of a circulating ring.