Abstract: Rotor - stator interaction noise is a crucial component of fan noise. The interaction noise between the rotor of axial cooling fan and the downstream strut is studied by means of numerical simulation and experiment. In numerical simulation, the interior complex flow characteristics of the fan are captured by Large Eddy Simulation model, and the characteristics of far-field noise are modeled by ulilizing FW-H equation based on the acoustic analogy theory. The experiment was carried out in an anechoic chamber by using free-field microphones. The flow of the fan is changed by means of changing the windward width H of the downstream strut and making a slot, and the effect of different control strategies on the aerodynamic and noise characteristics of the fan is analyzed. The results show that: Subjected to the interaction of the downstream strut to the fan, the mean static pressure of pressure surface for the fan presents a periodic distribution in the middle of the blade. The decrease of the width H and the increase of the perforation rate SP of the strut can effectively reduce the mean static pressure of the strut and the RMS pressure. The interaction noise is related to the leakage vortex between the rotating outer ring of the fan and the downstream strut. The two different control strategies can suppress the generation of vortex and reduce the discrete noise. Good agreement is obtained between the simulation and the experiment, and both results show that the maximum noise reduction of more than 5 dB can be achieved at the Blade Passing Frequency (BPF) under the cases that we have tested.