The invention relates to a method for synthesizing olefin by selective desaturation of inert carbon-carbon bonds. The method comprises the following steps of: synthesizing a chlorinated amide compound serving as a raw material in the presence of visible light, a ruthenium catalyst and a ligand, and post-treating reaction liquid to obtain a remote alkenyl amide compound. In the presence of the ruthenium catalyst and the phenylpyridine ligand, intramolecular carbon-hydrogen bond activation of the amide compound is successfully realized, and the remote olefin compound is synthesized; according to the method, chloro-amide which is simple and easy to obtain is used as a raw material, the substrate application range is wide, and the reaction efficiency is high; in the free radical migration process, 1, 5 migration occurs all the time along with beta-H elimination, terminal alkene and conjugated double bonds are used as main products, and high regioselectivity is achieved; and the maximum E / Z value of the obtained olefin compound is greater than 20: 1, and the stereoselectivity is good. The double bond of the compound can be further converted into other functional groups, the conversion process is simple in one step, and the obtained derivative can be used as a medical intermediate and has high potential application value.