In this letter, we reported a high performance quasi-vertical GaN Schottky Barrier Diode (GaN SBD) on sapphire substrate by combining Argon-ion implantation with Oxygen plasma termination, the leakage current density of the device decreases by about an order of magnitude in reverse 25-75 V compared with Argon-ion implantation alone. The turn-on voltage of the device is only 0.46 V, the ideal factor η = 1.05, and the specific on-resistance is 1.01 mΩ·cm 2 , while high ION/IOFF (∼10 9 ) and large breakdown voltage (190 V) are maintained.