Abstract: The aim is to study the changes of four phenolic acids in the leaves of maize seedlings before and after drought stress. The content of gallic acid, coumalic acid, chlorogenic acid and caffeic acid were quantitatively determined by High Performance Liquid Chromatography (HPLC), Thermo Scientific Syncronis C18 column (4.6 mm × 250 mm, 5 μm) as analytical column, acetonitrile- 0.5% acetic acid solution with gradient elution, 1.0 mL/min flow rate, 280 nm detection wavelength and 30℃ column temperature. The results showed that the linear relationship between peak area and 1-100 mg/L gallic acid, coumalic acid, chlorogenic acid and caffeic acid was good, the correlation coefficients (R2) were greater than 0.999. Adding standard recovery and precision RSD fulfilled the analysis requirements. The coumalic acid content was relatively high and gallic acid content was relatively low. After drought stress, the contents of the other three phenolic acids decreased except caffeic acid. The contents of four phenolic compounds in different varieties of maize seedlings was different and changed differently under drought stress, which was related to its sensitivity to drought.