The present invention provides a method for preparation of an 1-alkene-acrylate based copolymer comprising a step of a radical polymerization reaction of 1-alkene and acrylate based monomer under presence of a metal oxide or Lewis acid, and a method for preparation of an alkene-acrylate based copolymer comprising reacting alkene with an acrylate based monomer under presence of a metal oxide. In the method of preparation according to the present invention, the process is simple and properties of the copolymer can be easily controlled by preparing the copolymer in a mild condition of 100° C. or less and 200 bar or less. In addition, the amount of the polar group of the copolymer prepared by the method is so high that the copolymer can be used for transparent optical products. Since the alkene-acrylate based copolymer prepared by the method is a random copolymer of ethylene and a polar monomer and the amount of the polar group of the polar monomer so high that the crystallinity of the ethylene monomer does not remain in the copolymer, the ethylene-acrylate based copolymer is not affected from a transparency of the polymer and thus may be used for optical products.