The invention provides an ion migration spectrometry-based trimethylamine detection method. According to the method, the ion migration spectrometry detection in a positive ion mode is adopted; a volatile ketone material is taken as a doping agent; the doping agent is carried into an ion migration spectrometry ionization region through a carrier gas or a floating gas of the ion migration spectrometry; trimethylamine sample molecules are carried into an ion migration spectrometry reaction region through the carrier gas or the floating gas and form a specific reaction reagent ionic reaction with the doping agent to form characteristic trimethylamine product ions; the product ions enter a migration region through an ion gate which is opened by a pulse, are separated in the migration region according to the different migration rates, are detected in a Faraday plate, and finally are received and detected by a signal receiving and detecting system to form a typical ion migration spectrometry spectrogram. The detection method provided by the invention has the advantages of high sensitivity, high selectivity, simple operation and the like, and can realize quick detection of ppb-magnitude trimethylamine.