The invention discloses a detection method of benazolin acetic acid in plant-based food. The detection method comprises the following steps: step I, extracting benazolin acetic acid in a sample; step II, purifying the extracted liquid through a mixed anion exchange column; step III, detecting a benazolin acetic acid standard product by adopting liquid chromatogram to be matched with an ultraviolet detector; step IV, establishing a benazolin acetic acid standard curve; and step V, detecting the purified sample by adopting the method in the step III, and calculating the content of the benazolin acetic acid in the sample to be detected according to the standard curve. By adopting the detection method, the current situation that no method is used for detecting the benazolin acetic acid in the plant-based food at present can be solved. The detection method is strong in impurity interference resistance, and is accurate, reliable, sensitive and quick.