The invention discloses a boron-free chlorine-free formaldehyde-free microemulsified cutting fluid and application thereof. The microemulsified cutting fluid is prepared from the following raw materials in percentage by mass: 30-60% of base oil, 1-5% of rust inhibitor, 0-5% of extreme pressure agent, 1.5-8% of bactericide, 3-15% of mixed base, 0-5% of coupling agent, 1-8% of anti-hard water agent, 1.2-5% of corrosion inhibitor, 5-20% of lubricant, 3-15% of anionic surfactant, 3-20% of emulsifier and the balance of water. The microemulsified cutting fluid disclosed by the invention has excellent lubricating properties, and can simultaneously satisfy multiple processing modes, including fraising, boring, tapping, threading, high-speed milling, hole drilling and the like. The microemulsified cutting fluid is especially suitable for processing electronic aluminum alloys. In addition, the microemulsified cutting fluid has the advantages of excellent defoaming property, excellent wettability, high raw liquor stability, high emulsifying stability, high biological stability, longer service life, lower consumption and lower cost.