The invention discloses a multi-layer 
proton exchange membrane for water 
electrolysis, the multi-layer 
proton exchange membrane comprises a five-layer structure which sequentially comprises a long 
side chain perfluorinated 
sulfonic acid resin layer, a short 
side chain perfluorinated 
sulfonic acid resin layer, a microporous layer, a short 
side chain perfluorinated 
sulfonic acid resin layer and a long side chain perfluorinated sulfonic acid resin layer, and the preparation method comprises the following steps: firstly, dissolving long side chain resin and short side chain resin to prepare a membrane 
casting solution; secondly, filling the long-side-chain perfluorinated sulfonic acid resin solution and the short-side-chain perfluorinated sulfonic acid resin solution into a 
coating die head for layered 
coating and film forming; laying a 
polytetrafluoroethylene microporous membrane again, and carrying out layered 
coating on the long and short side chain perfluorinated sulfonic acid resin solution to obtain a 
composite structure; and rolling and laminating the prepared composite layer II to obtain the multi-layer 
proton exchange membrane for water 
electrolysis. The proton exchange membrane disclosed by the invention is better in uniformity; the long side chain resin and the short side chain resin are alternated, so that 
high conductivity under low IEC can be realized, the proton exchange 
composite membrane has relatively good 
chemical stability, dimensional stability and relatively 
high conductivity, and the problems of poor proton 
conductivity and short service life in the operation process are solved.