The invention discloses a method for determining the content of phorone in Nicodil by gas chromatography-mass spectrometry, which comprises the following steps of: 1, preparing a reference substance solution, precisely weighing a phorone reference substance, putting the phorone reference substance into a volumetric flask, dissolving the phorone reference substance to a scale by using a diluent, and uniformly shaking; 2, preparing a test solution, precisely weighing a dinitrandil raw material medicine, putting the dinitrandil raw material medicine into a volumetric flask, dissolving the dinitrandil raw material medicine to a scale by using a diluent, and uniformly shaking; 3, taking the diluent as a blank sample, and placing the diluent in a volumetric flask; and 4, precisely measuring the test solution and the reference solution, performing sample introduction, performing separation analysis by adopting a gas chromatograph-mass spectrometer, and recording a spectrogram. The detection method provided by the invention is verified by a test, and a result shows that the method is strong in specificity, good in precision and high in accuracy, and can be used for rapidly determining the content of the phorone in the Nicodil.