Salt-resistant high-calcium-magnesium-resistant anionic-nonionic surfactant

The invention provides a salt-resistant high-calcium-magnesium-resistant anionic-nonionic surfactant, wherein the anionic-nonionic surfactant is a fatty alcohol-polyoxyethylene ether carboxylate typesurfactant, the molecular general formula of the anionic-nonionic surfactant is RO (CH2CH2O) n-1CH2COOM, M is a metal ion, R is an alkyl group with 20-22 carbon atoms, and n is the sum of ethoxy groups and is any integer selected from 10-15. A series of anionic-nonionic surfactants are synthesized, fatty alcohol-polyoxyethylene ether carboxylate with high salt resistance is obtained through screening, the crude oil recovery rate is greatly increased, and the anionic-nonionic surfactant is particularly suitable for high-temperature and high-salt oil reservoirs; in addition, the invention also optimizes the preparation method of the fatty alcohol-polyoxyethylene ether carboxylate. Experiments show that the fatty alcohol-polyoxyethylene ether carboxylate type anionic-nonionic surfactant provided by the invention has