The invention discloses a p-type diamond high-low barrier Schottky diode and a preparation method thereof. The p-type diamond high-low barrier Schottky diode comprises a diamond substrate, and is characterized in that one surface of the diamond substrate is provided with a diamond epitaxial layer, and the other surface is provided with a ohmic contact electrode; the surface of the diamond epitaxial layer is provided with a microstructure in which convex beams and channels are alternatively distributed; the surface of the convex beams is provided with an oxygen terminal surface, the oxygen terminal surface is provided with low barrier Schottky region metal; the area except for the surface of the convex beams in the microstructure of the diamond epitaxial layer is provided with a fluorine terminal; and the low barrier Schottky region metal and the surface of the fluorine terminal are provided with a layer of high barrier Schottky region metal. Compared with the prior art, a Schottky diode with small forward turn-on voltage, high current density, small reverse leakage current and high breakdown voltage simultaneously can be acquired according to the invention.