Disclosed is a microemulsifying metal-cutting-fluid composition, comprising base oil or oily agent, mixed alcohol-amine, boric acid, anionic surfactant, nonionic surfactant, antirust agent, copper alloy corrosion inhibitor, preservative, deionized water and the like. The invention has the advantages of excellent lubricity, cooling ability, cleaning ability and a long lifetime of metal cutting fluid, being suited to various metal processing technologies such as cutting, reaming, boring, grinding. Also, the wastewater is easy to treat.