Abstract: The large eddy simulation technology and FW-H method were used to numerically simulate the unsteady turbulent flow field and its far-field radiation noise in a centrifugal blower, so as to analyze the influence law and mechanism of the parameters of slot at leading edge of diffuser blade on the noise features of the blower. Results show that the diffuser with slotted structure could suppress or delay the separation of boundary layer on the surface of diffuser blade, which makes the flow become more uniform and thereby suppresses the origination of flow noise. The noise features of a centrifugal blower are related to the geometrical parameters of the slot at leading edge of the blade. In the case of relative slot length L/C=0.3 and relative slot height h/H=0.1, the total sound pressure level of all measuring points could be reduced by up to 20 dB. It can be seen that the model with fixed relative slot height and variable relative slot length has better noise reduction effectiveness than that with fixed relative slot length and variable relative slot height.