Based on the characteristics of blowing control, a new technique was put forward to weaken slat cove separation and reduce farfield noise. The effect of the slat blowing control on lift performance, the flow field and noise spectra with a three-element high-lift aerofoil was investigated by using the computational fluid dynamics(CFD) code of Fluent, the Reynolds-averaged Navier-Stokes equations and FW-H acoustic analogy. The blowing holes were set on the lower surface of the slat. By using the slat blowing technique, the slat cove separation can be controlled efficiently and the lift coefficient increased. The aerodynamic performance varies with different blowing coefficients. As compared to the baseline configuration, the noise content in low-frequency range in blowing control cases is reduced by 2～4.5dB on the average.