In this study, we report the GaN-based LEDs with Ni/Ag (1nm/100nm) layers underneath an insulating SiO2 layer. It is confirmed that the Ni/Ag mirror shows good thermal stability and the reflectance of Ni/Ag is 90.6 % after thermal annealing at 500°C for 5 min. We can not only achieve much better current spreading but also prevent the light absorption by the opaque p-pad electrode. With 20 mA current injection, it was found that output power of the LEDs with SiO2/Ni/Ag layers was 6.5 and 12.1% larger than those of the LEDs with a SiO2 layer and without the SiO2 layer, respectively. Furthermore, the 20 mA forward voltage only increased slightly from 3.03 to 3.07 V for the LEDs with SiO2/Ni/Ag layers.