The invention provides a synthesis method of 2-methylene glutaronitrile. According to the method, tricyclohexylphosphine is taken as a catalyst; an acrylonitrile dimer is chemically catalyzed under the condition with a solvent or not; the dosage of the catalyst is 0.1-5.0 wt%; the reaction temperature is 50-90 DEG C; and the initial concentration of the acrylonitrile is 3.0-15.2 mol/L. Furthermore, the reaction product is purified in a distilling manner. The method is available in materials, mild in reaction condition, high in yield, good in selectivity, strong in atom economy, friendly to the environment and applicable to industrial production.