Abstract: The present invention pertains to the technical field of energy resource chemical industry, and in particular relates to a process for producing polyoxymethylene dimethyl ethers by directly using concentrated formaldehyde aqueous solution as feedstock to catalytically react with methanol and/or methylal in a fixed bed reactor. The method of the present invention uses concentrated formaldehyde aqueous solution with a concentration of over 80% by weight to react with methanol and/or methylal, in the presence of an acidic catalyst, to produce the required polyoxymethylene dimethyl ethers.