The invention relates to an electrolysis diaphragm. The electrolysis diaphragm comprises a fabric and a coating applied to the fabric, wherein the fabric is made from, by weight, 30-100 parts of short polyphenylene sulfide fibers and 0-70 parts of short polyphenylene sulfide fibers. The invention further provides a preparation method of the electrolysis diaphragm and application of the electrolysis diaphragm in water electrolysis for hydrogen production and water electrolysis for oxygen production and in a chlor-alkali electrolysis bath by serving as a non-asbestos diaphragm. The heat-resistant performance of the diaphragm is improved, the prolonging of the service life of the non-asbestos diaphragm is promoted, and the efficiency is improved.