Disclosed is a method for synthesizing a beta-hydroxy propionic acid. The method includes preparing propenoic acid into a propenoic acid solution with a mass fraction of 10% to 60% with water, adding polymerization inhibitor hydroquinone accounting for 0.1% to 1.0% of the quality of the propenoic acid, adding a catalyst to regulate the pH to be 0.5 to 4.0, replacing air in a kettle with nitrogen gas, reacting the mixture at a temperature of 60 DEG C to 280 DEG C for 1h to 24h, and cooling the mixture to a room temperature to obtain the beta-hydroxy propionic acid. The method for synthesizing the beta-hydroxy propionic acid has the advantages that raw materials are cheap and easy to obtain, reaction conditions are mild, technological conditions are simple, resultants are easy to separate, the reaction is provided with high yield, and defects that other chemical method materials are difficult to obtain and the biological method yield is low are overcome.