It is used as raw material for synthetic resin and coating, as well as impregnant, dispersant and lubricant in petroleum industry, fabric, plastic and paper industry, and as plasticizer for PVC resin and methacrylic resin. Maleate is used as an intermediate in organic synthesis, mainly in addition reaction on double bond. For example, Diels alder reaction is carried out with butadiene and cyclopentadiene to add compounds containing active hydrogen such as hydrogen, nitrile, mercaptan and amine. The famous surfactant dialkyl succinate sulfonate is prepared by the addition of sodium bisulfite. When other ammonia and amines are added with maleate, they undergo amidation (amidation) reaction due to ammonolysis, that is, they play the role of acylating agent. Diethyl maleate is widely used. It is also used as an intermediate in the production of pesticides and medicine such as marathon, and also in the production of polymer compounds; Dimethyl maleate, dibutyl ester and dioctyl ester are excellent plasticizers for PVC; It can be copolymerized with vinyl chloride, vinyl acetate and other monomers and used as coating, adhesive, impregnating agent, dispersant and lubricant for papermaking and fabrics; Diisooctyl maleate and dinonyl maleate are good petroleum pour point depressants.