The invention relates to a method for preparing meropenem. The method provided by the invention comprises the following steps of: respectively adding (1R,5R,6S)-6-[(1R)-1-hydroxy]-1-methyl-2-diphenylphosphoacyloxy-carbapenicill-2-ene-3-p-nitryl phenyl carboxylate, (2R,4S)-4-sulfydryl-2-dimethylaminoformoxyl-1-p-nitryl phenyl carbonyl pyrrolidine and alkaline quaternary ammonium salt into a reaction bottle, and agitating for reaction; tracking by utilizing TLC (Thin-Layer Chromatography) and adding 5 wt% Pd (Palladium)/C (Carbon) catalyst after the reaction is finished; importing hydrogen gas for reduction, and tracking by utilizing the TLC; after the reaction is finished, extracting by utilizing toluene to separate out an organic layer; then drying and concentrating; and crystallizing by utilizing isopropanol to obtain a solid product. Compared with the prior art, the method provided by the invention has the advantages as follows: a quaternary ammonium alkali catalyst and a homogeneous catalysis one-pot method reaction technology are used in the reaction process, the technological operation is simplified and no pollution is generated to the environment.