Abstract: Aiming at the aero-acoustics problem of an axial flow fan, the aerodynamic and acoustic characteristics of the axial flow fan are analyzed by using Detached Eddy Simulation (DES) and the acoustic analogy method. Based on the semi-anechoic chamber of AVIC Aerodynamic Research Institute, the noise is tested to verify the reliability of the numerical method. By analyzing the reasons for noise production, the design direction is determined. By modifying the structure of the moving blades and adjusting the mounting angle of the stationary blade, the aerodynamic noise of the fan is optimized, and the effect is analyzed. The results show that tip leakage flow leads to a larger low-pressure zone in the 1/3 chord length of the blade, causing severe flow separation around the trailing edge of the stationary blade, resulting in higher tonal noise at 1BPF and higher broadband noise in the range from 5000 Hz to 8000 Hz for this axial flow fan. By changing the shape of the blade and adjusting the mounting angle of the stationary blade, the strength of the tip leakage flow vortex is reduced, and the interaction between the tip leakage flow vortex and the stationary blade is weakened. The noise at 1BPF, 2BPF, and 3BPF is reduced. The total noise reduction at a specific monitoring point reaches up to 2.2 dBA.