The invention discloses a device for electrolyzing water with proton exchange membrane and providing highly pure hydrogen and oxygen for fuel cell. The device sequentially contains front side plate, diffuse plate, electric conduction plate, front special plate, H/O flow field plate, membrane electrode, and back special plate, baffle plat and rear side plate. Each of the units is round pressure-proof structure. Water, gas flow field and electric conduction plate adopts Ti alloy and other corrosion resistant alloy. Membrane electrode diffusion layer adopts carbon paper or cloth. The membrane electrode is high active 0 pole pitch electrode prepared by hot briquetting proton exchange membrane and composite Pt catalyst. The working medium of the invention is pure water, has no pollution to theenvironment, and can be recycled. The hydrogen and oxygen obtained from the invention has high purity and do not need complex purification treatment. Regenerative fuel cell energy storing system withhigh specific energy prepared by combining the invention and fuel cell can be used in various kinds of main power source and dynamical systems in spaceflight and aerobat.