The invention provides a method for analyzing potassium (R)-[(3-ethoxy-1-methyl-3-oxoprop-1-enyl)amino]phenylacetate. A high performance liquid chromatography method is adopted for determining the content of D-phenylglycine and potassium (R)-[(3-ethoxy-1-methyl-3-oxoprop-1-enyl)amino]phenylacetate in a potassium (R)-[(3-ethoxy-1-methyl-3-oxoprop-1-enyl)amino]phenylacetate tested sample. A C18 chromatographic column is adopted, a mixed solution of acetonitrile and isopropanol or acetonitrile and tetrahydrofuran or acetonitrile and dioxane is adopted as a mobile phase, a reference substance solution and a tested sample solution are prepared, octadecylsilane bonding silica gel is adopted as a filler, and under appropriate chromatographic conditions, the tested sample solution and the reference substance solution are precisely measured and injected into a liquid chromatograph separately; chromatograms of the tested sample and a reference substance are recorded, and peak areas are calculated according to an external standard method to obtain the content of D-phenylglycine and potassium (R)-[(3-ethoxy-1-methyl-3-oxoprop-1-enyl)amino]phenylacetate in the tested sample. The operation process is simple and convenient, the precision is high, the stability is good, and the influence of impurities on measurement results can be effectively avoided.