In the continuous galvanizing line, gas knives are used to control the liquid coating thickness. They are based on the principle of turbulent planar impinging jet. The CFD (Computational Fluid Dynamics) method is used to research the turbulent planar impinging jet of gas knives. With the implement of FLUENT software, the realizable k-ε model is adopted to simulate the pressure field. The transverse impact pressure distributions on the steel strip are demonstrated. For gas knives with even nozzle slot, the plot of impact pressure is analogous to parabola, reducing from middle to two ends. This numerical result shows agreement with experimental one. It indicates that the realizable k-ε model can accurately predict the impinging jet. Besides, for gas knives with uneven nozzle slot, the impact pressure is basically equivalent. Furthermore, several main factors having effect on the coating thickness are studied. The numerical results reveal that, the higher the inlet pressure, the thinner the coating; and the longer the distance between jet and strip, the thicker the coating.