The invention relates to a single aspheric lens for laser Gaussian beam shaping and belongs to the technical field of laser beam shaping. The single aspheric lens successively comprises a lens front surface and a lens rear surface in the beam incident direction. The lens front surface is an aspheric surface, the lens rear surface is a plane, and a lens side surface is a cylindrical surface. The lens front surface protrudes towards the beam output direction. The material of the lens is SK2 optical glass. The single aspheric lens is used for shaping a red light beam with light intensity distribution of I(y) = I0exp (-2y<2>/y0<0>) and a Gaussian spot radius of y0 = 30mm, wherein I0 is central light intensity and is an arbitrary constant value. An outgoing beam is a flat-topped beam with and a spot radius of 36mm.