The invention relates to a method for synthesizing polyoxymethylene dimethyl ether. The invention mainly solves the following problems of the prior art that: in the process of synthesizing polyoxymethylene dimethyl ether, catalyst separation is difficult, the material conversion rate is low, and product selectivity is poor. The method adopts methanol and trioxymethylene as materials, the reactiontemperature is 70 DEG C to 200 DEG C, the reaction pressure is 0.5MPa to 6MPa, the materials react with super solid acidic catalyst by way of contact, so that the polyoxymethylene dimethyl ether CH3O(CH2O)nCH3 is produced, wherein the used catalyst is selected from solid superacids. By weight part, the polyoxymethylene dimethyl ethe comprises the following components: (a) 20 to 70 parts of acid selected from sulfuric acid, hydrochloric acid or peroxosulfuric acid or at least one of salt thereof; (b) 30 to 80 parts of carrier selected from at least one of ZrO2, TiO2, SiO2, Fe2O3, SnO2, WO3 andAl203. The method effectively solves the problems, and can be used in the industrial production of polyoxymethylene dimethyl ether.