The invention discloses a synthesis method of a midbody 2-methyl quinoline. The synthesis method comprises the steps that aniline, 2-butenal, hydrochloric acid, concentrated sulfuric acid, sodium hydroxide, manganese chloride, pyrrole, tetraphenylporphyrin, stannous chloride and p-nitrobenzaldehyde serve as raw materials, aniline and 2-butenal are subjected to a cyclizing addition reaction to obtain 2-methyl quinoline under the effect of the catalyst Pt-SnO2 / C. Compared with the method that only manganese chloride serves as the catalyst, the obtained cyclizing addition effect is not ideal, theconversion rate and the yield are lower, while by adopting the homogeneous catalyst Mn / Sn-TPP to conduct epoxidation of 2-butenal, the conversion rate and the yield are greatly improved, meanwhile, the technology is green and environmentally friendly, no waste liquid is generated, the synthesis method meets the potential conditions of industrialized production, and both the purity and the yield of the product reach the ideal effect.