The invention relates to a processing equipment system and a processing method for preparing polyoxymethylene dimethyl ether (DMMn) using aqueous solution of formaldehyde as initial reaction raw material by continuous acetalation reaction. The reaction system of the present invention comprises a polymerization unit, an acetalation unit, a product separating unit and a catalyst regenerating unit. The process of the present invention uses aqueous solution of formaldehyde as initial reaction raw material, and has the advantages of high formaldehyde utilization rate, and cheap and easily available raw materials; polymerization and acetalation reaction employ ionic liquid as catalyst, and thereby realizing that two different reactions are catalyzed by the same ionic liquid with simple catalyst system; the separating mode combines extraction and rectification, and thereby realizing effective separation of catalyst, by-product water, product and reaction raw materials.