Taking the rotation speed of mobile fan as the initial value of simulation, grids within the computational regions inside the air duct were divided into sections based on the dynamic reference model. The structure of air-blast sprayer was optimized by using numerical experiments and orthogonal experiment. The flow speed at the outlet of air duct was simulated. In order to verify the correctness of model, flow speed at the outlet of air duct was measured at each corresponding fan rotation speed. The coverage rate statistics and χ2-test were carried out between measured and simulated value. The results indicated that the order of factors which affected the duct pressure loss and outlet flow speed was: the diameter of outlet, the cylindrical duct length and the tapered duct length. Meanwhile, at the sampling spot of air duct outlet, the measured flow speed in simulation was 95%. The simulated flow speed at the air duct outlet was submissive with the measured distribution when χ2-test result was under 0.05. It was reliable to simulate outlet flow speed of air duct by using dynamic reference model with fan rotation speed as initial value. 