Green and environment-friendly metal cutting fluid and preparation method thereof

The invention relates to a green and environment-friendly metal cutting fluid as well as a preparation method and application thereof. The metal cutting fluid comprises the following components: 12-30% of base oil, 12-30% of a nonionic surfactant, 2-3% of an anionic surfactant, 10-25% of a composite anti-rust agent, 15-20% of a composite lubricant, 5-7% of monohydric alcohol, 0.1-0.2% of a defoaming agent, 0.8-2.5% of a bactericide and the balance of water. The preparation method comprises the following steps of: heating and mixing the composite anti-rust agent and part of water, cooling, adding the composite lubricant and an auxiliary anti-rust agent, mixing well, respectively adding the nonionic surfactant, the monohydric alcohol and the base oil, finally adding the other components, and stirring until the solution is clear, thereby obtaining the metal cutting fluid. Compared with the prior art, biodiesel prepared from illegal cooking oil is adopted as the base oil, reutilization of the illegal cooking oil