The invention relates to a method for simultaneously and rapidly detecting the contents of phenyllactic acid and 4-hydroxy phenyllactic acid by RP-HPLC. The method comprises the following steps: a, preparing a mobile phase; b, preparing standard phenyllactic acid and 4-hydroxy phenyllactic acid solutions with different dilution ratios, carrying out high performance liquid chromatography analysis on the standard phenyllactic acid and 4-hydroxy phenyllactic acid solutions by adopting a high performance liquid chromatograph, making a standard curve, and drawing a phenyllactic acid content-peak area standard curve and a 4-hydroxy phenyllactic acid content-peak area standard curve to obtain a standard curve regression equation; and c, properly diluting a sample solution containing phenyllacticacid and 4-hydroxy phenyllactic acid, carrying out centrifuging for 2 to 4 minutes at the speed of 8000 to 10000r/min, carrying out 0.22 m microfiltration after centrifuging, carrying out high performance liquid chromatography analysis by adopting chromatographic conditions which are completely the same as those of the standard solution in the step b, and calculating the contents of phenyllactic acid and 4-hydroxy phenyllactic acid by utilizing an internal standard method according to the peak area and the standard curve regression equation in the step b.