The invention discloses a method for monitoring level of paraben comprising: dissolving a sample in a solvent and obtaining a supernatant containing paraben by ultrasonic vibration and high speed centrifugation; performing a derivatization reaction between a derivatization reagent and paraben by adding the derivatization reagent into the supernatant to obtain a derivatization solution containing a tagged paraben; extracting the derivatization solution by an extractant to obtain an extract containing the tagged paraben; and ionizating the tagged paraben by a laser beam and analyzing mass-to-charge ratio of the tagged paraben by an analyzer to determine molecular weight thereof.