The invention provides a method for preparing mono-methyl succinate. The method comprises the following steps: carrying out a mono-esterification reaction on succinic anhydride and methanol in a static mixer, conveying the reaction effluent into a high gravity reactor, and meanwhile filling water vapor into the high gravity reactor; cooling and separating the liquid material after the reaction to obtain mono-methyl succinate. The method for preparing mono-methyl succinate provided by the invention is reasonable in craft process, simple in separation method, high in product purity, good in quality and high in yield.