Abstract: Effects of leading-edge shape on stability and transition of three-dimensional hypersonic boundary layer over a flat-plate blunt delta wing with large sweep angles were studied by using linear stability theory (LST) analysis. The results indicate that the effects of the elliptic leading angles shapes on basic flow properties and stability characteristics only exist at regions nearing the leading edge. As the semi-axis ratio of the leading edge cross section (the shape factor of elliptic leading edge) increases, the shape of leading edge becomes sharper, the cross flow velocity and growth rate of disturbance wave are strengthened. However, influences of sharpening the shape of the elliptic leading edge on neutral points of different modes are different, which are postponing for cross modes and first modes, and barely moving for second modes. As a result, the transition location, which is dominated by first modes, moves backward as the shape of leading edge becomes sharper.