The invention relates to the preparation technology of heterojunction ultraviolet laser diodes, in particular to a method for preparing pointed-cone-shaped p-NiO (nickel oxide) / n-ZnO (zinc oxide) heterojunctions by combining the film coating technology and the femtosecond laser technology. According to the method, firstly, heat oxidation is utilized to form a NiO layer on a nickel sheet, then, an atomic layer deposition method is utilized for preparing a ZnO layer, next, an ITO (indium tin oxide) transparent upper electrode is formed outside the n-type ZnO layer by a sputtering method, finally, a pointed-cone-shaped array is formed on the nickel sheet covered with an NiO / ZnO / ITO layer by the femtosecond laser processing technology, pointed-cone-shaped p-NiO / n-ZnO heterojunctions are formed, voltage is applied to the ITO and the bottom of the nickel sheet, and the electroluminescence can be realized.