A disclosed novel composite metal polishing fluid is characterized by being prepared from the following raw materials in parts by weight: 11-13 parts of cerium oxide, 2-4 parts of graphene oxide, 7-9 parts of rapeseed oil, 1-2 parts of stannous octoate, 4-6 parts of polyoxyethylene sorbitan fatty acid ester, 3-5 parts of polyoxyethylene castor oil, 4-6 parts of urea, 2-4 parts of citric acid, 4-6 parts of emulsified silicone oil, 5-7 parts of an auxiliary agent, and 300 parts of deionized water. The prepared mixed polishing fluid is safe, non-toxic and reasonable in formula. Through the cooperation of the added surfactant and the abrasive, the polishing effect is improved, preferential adsorption is realized, and a long-term easily-cleaned physical adsorption surface is formed. By adding the auxiliary agent, the polishing fluid has good dispersity, lubricity and film-forming property, and is capable of forming an air-obstructing layer on a workpiece surface to prevent air from corroding a metal surface. The polishing fluid is capable of satisfying the polishing processing requirements of various products and parts, and helps to improve the polishing efficiency, cleaning effect, surface precision and the like.