The invention provides an 
ion mobility 
spectrometer and a carrier gas flow control method thereof. The 
ion mobility 
spectrometer comprises a migration tube used for completing 
ion migration, an 
ionization source used for generating 
reagent ions, a sample 
introduction device used for conveying a sample gas into the migration tube, a 
molecular sieve used for 
drying and purifying a carrier gas, and a flow 
control unit, a 
temperature control unit, a 
humidity sensing unit and a processor unit, which are used for measuring and controlling temperature, 
humidity and the carrier gas flow. According to the ion mobility 
spectrometer provided by the invention, a humidification 
bottle and a flow valve are arranged to adjust and control the 
humidity of the carrier gas in the migration tube, and humidity sensors are arranged at a gas outlet of the migration tube and an outlet end of the 
molecular sieve to compare a humidity difference detected by the two and judge whether the 
molecular sieve is ineffective or not; an expert assistance PID control method is used for controlling the carrier gas flow, in order to improve the control precision and stability of the carrier gas flow; and the ion mobility spectrometer provided by the invention adopts an 
embedded design, thereby being convenient to use, strong in flexibility and suitable for onsite application.