Ethylene copolymer and method for preparation thereof and composition and crosslinked polymer and tire

An ethylene copolymer, wherein the ethylene copolymer comprises an ethylene structural unit derived from ethylene and a conjugated diene structural unit derived from a conjugated diene;

• based on the total amount of the ethylene copolymer, the content of the conjugated diene structural unit is 30-45 mol %, and the content of a 1,2-polymerized vinyl structural unit formed by 1,2-polymerization of the conjugated diene and having side chain double bonds is 20-40 mol %;
• the total amount of a 1,2-polymerized structural unit is 95 mol % or more based on the total amount of the conjugated diene structural unit in the ethylene copolymer, and the ethylene copolymer has a weight average molecular weight of 30,000 to 300,000, wherein 1,2-polymerized structural unit comprises a 1,2-polymerized vinyl structural unit formed by 1,2-polymerization of the conjugated diene and having side chain double bonds, a 1,2-cyclopropane ring structural unit formed by 1,2-polymerization of the conjugated diene and having a cyclopropane ring, and a 1,2-cyclopentane ring structural unit formed by 1,2-polymerization of the conjugated diene and having a cyclopentane ring.