Abstract: A numerical analysis of the flow field about sweep forward blades has been carried out.Time marching method is used to calculate the three dimensional inviscid flow field.Boundary layer parameters are calculated with integrated boundary layer equations in non orthogonal axises.The calculated results show that in axial compressors and fans with sweep forward blades the intensity of passage vortex,secondary flow and tip losses are decreased,the early separation from the blade surface is protected,the flow field in tip area is improved obviously.As a result,the aerodynamic efficiency of axial compressor or ventilator is enhanced.