The present invention discloses a method for rapid on-site detection of fentanyl analogs using a miniature mass spectrometer, comprising the following steps: (1) selecting a spotting plate; (2) loading a sample: depositing the sample and 3-nitrobenzonitrile solution in acetonitrile on the spotting plate to form a crystalline mixture; (3) carrying out analysis and detection: setting the parameters of the miniature mass spectrometer, placing the crystalline mixture on the spotting plate in close proximity to the inlet of the miniature mass spectrometer, and facilitating the ionization of the crystalline mixture for the analysis and detection of fentanyl analogs. The method for rapid on-site detection of fentanyl analogs using a miniature mass spectrometer provided by the present invention requires no extraction solvent, no voltage, no laser, no gas, and the method is simple, rapid, and suitable for rapid on-site detection of fentanyl analogs.