Abstract: The 3-D incompressible steady time-averaged N-S equation,continuity equation and k-ε turbulence model equations are applied to calculating the flowfield in the cascade passage with circumferential grooved casing treatment.The mechanism of extending stability of the circumferential grooved casing treatment is elaborated by means of a 3-D viscous numerical simulation.It is revealed that a pressure difference between suction side and pressure side induces a strong gas flow which is absorbed in the pressure side and poured out from the suction side.This flow can blow off the low energy boundary layer efficiently to retard the stall emergence.The physical model and the flow pattern of the flowfields affected by inductive velocities are described.This is a new approach to analysis and design of the compressor casing treatment.