We present a high-quality Ni/Ag/Pt Ohmic contact to p-type GaN. After the sample is annealed at 500℃ in O2 ambient for 3min, a specific contact resistance as low as 2.6×10-5Ω·cm2 and an optical reflectivity of 82% at 460 nm are obtained. The Auger electron spectroscopy analysis shows that the Pt layer can improve the surfacemorphology and thermal reliability of the annealed Ag-based electrode, Ag plays a key role in achieving goodohmic contact due to the outdiffusion of Ga into Ag forming Ga vacancies which increase the hole concentration,while the surface contamination of p-type GaN is reduced by Ni.