A new method is presented to calculate the flow around an airfoil with separation.The airfoil configuration is arbitrary and is transformed to a circle by conformal mapping tech-nique.The model of separated flow,which was proposed by Jacob,is adopted here,and the po-sition of the separation point and the pressure on the airfoil are calculated by iterative coupling ofpotential flow and boundary layer.The effects of boundary layer are simulated by modificationof boundary condition.All iterative procedures converge rapidly because of using Fast FourierTransform(FFT). A new method is presented to calculate the flow around an airfoil with separation. Airfoil configuration is arbitrary and is transformed to a circle by conformal mapping tech-nique.The model of separated flow, which was proposed by Jacob, is adopted here, and the po-sition of the separation point and the pressure on the airfoil are calculated by iterative coupling of potential flow and boundary layer. The effects of boundary layer are simulated by modification of a boundary condition. All iterative procedures converge rapidly because of using Fast Fourier Transform (FFT) .