A corrosion-free anti-wear semi-synthetic cutting fluid is prepared from the following raw materials: 12-14 parts of mineral oil, 3-4 parts of ricinoleic acid, 1-2 parts of diethanolamine, 10-12 parts of isopropanol, 3-4 parts of polyoxyethylene fatty acid, 1-2 parts of diamond nanometer particles, 1-2 parts of pentaerythritol, 2-3 parts of lauryl alcohol polyoxyethylene, 0.05-0.1 part of lanthanum acetate, 6-8 parts of an auxiliary agent and 200 parts of water. The cutting fluid provided by the invention has excellent antiwear performance by employing diamond nanometer particles; and the cutting fluid has the advantages of good lubricity and good cleaning performance, is stable in emulsion system, good in settlement resistance, does not corrode machine tools, is not easy to deteriorate and reek, and is long in service life.