A conformal boron doping method for a three-dimensional structure includes the steps of: removing a natural oxide layer on a surface of a silicon-based three-dimensional substrate; forming a buffer layer on the surface of the silicon-based three-dimensional substrate; forming a boron oxide thin film on the alumina buffer layer; covering a passivation layer on a surface of the boron oxide thin film; and driving boron impurities containing boron oxide into the silicon-based three-dimensional substrate through the buffer layer by using laser or rapid annealing, to dope the silicon-based three-dimensional substrate. Selecting suitable boron source precursors and oxidants solves the problems of difficult nucleation and inability to form a film after reaching a certain thickness for boron oxide. By selecting alumina as the passivation layer, it is possible to protect the boron oxide thin film from being damaged, and thus achieve damage-free diffusion doping during laser or rapid annealing processes.