The invention provides an oxygen cathode ion-exchange membrane electrolytic cell and a mounting and sealing method thereof. The oxygen cathode ion-exchange membrane electrolytic cell is characterized by comprising a mechanical fixing device, an oxygen diffusion electrode, an elastomer gasket and a cell frame which are sequentially arranged from top to bottom, wherein the adjacent surfaces of the oxygen diffusion electrode, elastomer gasket and the cell frame are respectively coated with a base coat, an adhesive layer is coated on each base coat, and the adhesive layer and the base coats on the two sides form a bonding layer; the mechanical fixing device is fixed on the cell frame, and can form a compaction stress on the oxygen diffusion electrode and elastomer gasket to form a close seal with the cell frame; and the bare positions of the oxygen diffusion electrode, elastomer gasket and bonding layer in the electrolyte are respectively coated with a protective coat. The ion-exchange membrane electrolytic cell provided by the invention has the advantages of high mounting convenience, high production efficiency, reliable seal and strong concentrated alkali corrosion resistance, can effectively fix the oxygen diffusion electrode, and can ensure no electrolyte leakage in the actual electrolysis production process.