A flat-top thin-walled structure is formed on a special-shaped base surface using hollow laser-light internal powder-feeding technology. A method of fractal stratification is proposed to solve problems of lap defects of scanning initiating terminal and low efficiency when the traditional equal-high stratification is used on uneven special surfaces. This method uses the linear relationship among the cladding height, scanning speed, cladding layer width, and defocusing amount in a certain range. A segmented variable speed is used to achieve the segmented melting height, so that the substrate low point is raised and a flat top structure is gradually added on the top of the special-shaped base surface. Test results demonstrate that, by combining the base surface and interlayer, the top surface of the thin-walled structure is typically flat. It has a maximum absolute error of approximately 0.2 mm, with a size error within 8%; the forming region's microstructure is dense and uniform without obvious pores, cracks, or other defects;the range of microhardness is 685-720 HV.