A method for simultaneously detecting the concentrations of Prochloraz and Imazalil at relatively high concentrations was established with high performance liquid chromatography （HPLC） to scientifically standardize the use of Prochloraz and Imazalil in the preservation of citrus fruits.The results showed that the linear relationship between Prochloraz and Imazalil was good within the range of 5-300 μg/mL， indicating that this method has high sensitivity and accuracy.Prochloraz was stable at room temperature and Imazalil had a high rate of degradation in the post-harvest sorting line of Satsuma mandarins.The concentration of Prochloraz and Imazalil after 6 hours of processing 15 tons of Satsuma mandarins decreased by 98.6 μg/mL and 290.3 μg/mL， respectively.It is indicated that this method can be applied to detect the concentration of Prochloraz and Imazalil during the post-harvest processing of citrus fruits， which is beneficial for improving the efficiency of using fungicide and reducing costs of production.