Gallium oxide is a new generation of wide band gap materials, and its device has excellent performance. The barrier control of Ga₂O₃ Schottky diode by n⁺ high concentration epitaxial thin layer is studied. The results show that the performance of Schottky diode has greatly improved after epitaxy of n-type gallium oxide. The vertical current density is 496.88A·cm^–2, the reverse breakdown voltage is 182.30 V, and the calculated R_on is 0.27 mΩ·cm² when the epitaxial concentration is 2.6 × 10¹⁸ cm^–3 and the thickness is 5 nm. Further studies indicate that the current density increases with the increase of the layer thickness and the concentration. Theoretical analysis shows that the barrier is controlled by mirror force, series resistance and tunnel effect. Of them, the tunnel effect has the greatest influence, which makes the barrier height decrease with the layer concentration as \sqrt n and the thickness as \sqrt a. As a result, the hot emission current and the tunnel current increase simultaneously, which improves the performance of Ga₂O₃ Schottky diode.