In this paper, the multi-block patching and grid merging technique are adopted to generate computation grid for the complex structure of a jet device control channel. A Runge Kutta method with 5stage explicit scheme and a multi-grid method are applied to solve the flow model, which includes the whole N S equation, RNG kepsilon turbulence model and two layer zonal wall model. On the basis of numerical simulation and fluid field analysis, an improved scheme to the structure of control channel is put forward.