By taking the three dimensional (3D) air nozzle in the air blow off system of a level up machine as a study object, based on the basic equations of fluid mechanics and the RNG kε turbulence model, the mathematical air jet models were established. In order to study the effect of jet angle on the jet field, under the condition that other factors were the same, the jet angle was set as 90°、 60°、 45°、 30°respectively. Based on fluid simulation software, the jet field was analyzed under four different disposal conditions of the nozzle. The study shows that more air is blowing forward when the air nozzle is tilted at a certain angle, and the blow velocity increases. But the velocity component perpendicular to the plate decreases, and jet air impact pressure on the steel board is weakened. In the downstream of the impact point, strong eddy is appeared at the same time. According to the analysis, about 45°of an optimal jet angle is suggested.