The invention relates to a preparation method of high-purity cis-3,5-dimethylpiperidine, belonging to the field of organic synthesis. Using 3,5-lutidine as a raw material, 3,5-dimethylpyridine is obtained through catalytic hydrogenation reaction. The crude methylpiperidine is purified by precipitation to obtain high-purity cis-3,5-dimethylpiperidine, and its cis gas chromatographic purity is more than 99.5%. In the present invention, by introducing neutral alumina and alkali, the combination mode of pyridine molecules and catalyst molecules in the hydrogenation process is changed, which is beneficial to the generation of cis-isomers, and can obtain crude products directly used in pharmaceutical production; 99.5% of the cis isomer, there is no such high-purity report in the synthesis and separation of 3,5-dimethylpiperidine cis, in the synthesis and purification of piperidine derivatives and industrial production applications, it has greater Reference significance and high commercial value.