Gallium oxide, as a new generation of wide band gap materials, its devices has excellent performance. The barrier control of Ga2O3 Schottky diodes by n+ high concentration epitaxial thin layer is studied. The results show that the performance of Schottky diodes has greatly improved after epitaxy of n-type gallium oxide. The vertical current density is 496.88A/cm2; the reverse breakdown voltage is 182.30V, and the calculated Ron is 0.27mΩcm2 when the epitaxial concentration is 2.6×1018cm-3 and the thickness is 5nm. Further studies discover 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. Among them, the tunnel effect has the greatest influence, which makes the barrier height decreases with the layer concentration as and the thickness as . As a result, the hot emission current and the tunnel current collectively increase, which further improves the performance of Ga2O3 Schottky diodes.