Abstract: Gas-inducing reactors (GIRs) have been widely used in industry. The investigation of GIRs is important for their design and scale-up. The characteristics of gas-inducing impellers are compared with the traditional equipment. The gas-inducing impeller are classified on the basis of flow pattern and the basic principles of operation are introduced. The operation characteristics，the hydrodynamics and mass transfer performance of GIRs，including the critical impeller speed for the onset of gas induction，rate of gas induction，power consumption，gas holdup and mass-transfer coefficient are discussed. The future research on GIRs is prospected.