The invention discloses a cationic resin dephosphorizing method of oil and grease, which comprises the following steps: allowing sufficient contact of to-be-treated oil and grease with strongly acidic cationic resin, and removing phospholipid from the treated oil and grease through hydration dephosphorizing process to obtain dephosphorized oil and grease. The method of the invention adopts strongly acidic cationic resin to treat oil and grease. The sulfonic acid cation exchange resin has a solid strong acid property, and can convert a metal salt of phosphatidic acid to phosphatidic acid, which is removed by subsequent hydration dephosphorizing process. In this way, the method can remove both the hydrated phospholipids and non-hydrated phospholipids in oil and grease, so as to greatly improve the dephosphorizing effect of oil and grease and effectively ensure the quality of dephosphorized oil. The method has the advantages of short technical process, simple operation, and high dephosphorizing efficiency, and is economic and environmentally friendly.