The invention discloses a combined ion mobility spectrometry and ion trap mass spectrometry ionization cavity. The ionization cavity is composed of an ionization port, an introduction port, a reactionzone, an outlet port, an ion gate and a pinch valve and is used for connecting an ionization source, an ion mobility spectrometry and an ion trap mass spectrometry. Ions produced by the ionization source partially directly enter the ion mobility spectrometry through the ion gate, the other part enters the ion trap mass spectrometry through the pulse-type-opened pinch valve, and the ion mobility spectrometry and the ion trap mass spectrometry can be guaranteed to work simultaneously by an interface without mutual influence.