The invention relates to a water-soluble cutting fluid, which comprises the following raw material components by weight: 3-5% of monoethanolamine, 5-8% of triethanolamine, 2-5% of boric acid, 3-5% ofsebacic acid, 2-5% of tribasic acid, 15-25% of 25# transformer oil, 4-6% of pentaerythritol ester, 5-12% of a T702 anionic surfactant, 5-8% of a nonionic surfactant, 0.1-0.8% of a copper corrosion inhibitor, 0.3-1.0% of an aluminum corrosion inhibitor, and the balance of water. According to the present invention, the water-soluble cutting fluid is the universal water-soluble anti-hard water cutting fluid; the processing range of the water-soluble cutting fluid is wide, wherein the water-soluble cutting fluid can process cast iron, steel, stainless steel, copper alloys, aluminum alloys and a variety of metal materials; the water-soluble cutting fluid is generally suitable for soft water and hard water, can be used in all parts of the country, and has excellent hard-water resistance, whereinthe water-soluble cutting fluid can resist the hard water in Shandong area (the hard water rang is 500-1300); and with the independently researched and developed anticorrosion system, the product does not produce deterioration and odor changing within the service life of 1 year, and is environment-friendly .