The present invention discloses a preparation method of glycine. In the preparation method, chloroacetic acid and ammonia are used as raw materials; urotropine is used as the catalyst of the reaction; low-carbon alcohol solvent is used as a reaction medium; organic amine is added into the reaction system to be used as an acid binding agent; after the reaction is completed, the glycine with high content can be prepared through filtration. The preparation method solves the problems of the solvent that can not be recycled, serious solvent consumption, high cost, low yield, serious three-waste pollution and so on in the prior art. And the preparation method is suitable for the industrial production of the glycine.