The high-temperature operation up to 350°C of glass phosphor layer for using in converted white light-emitting diodes is demonstrated. The results showed that the phosphor-converted white light-emitting diode (PC-WLEDs) maintained good thermal stability in lumen, chromaticity, and transmittance characteristics at the high temperature up to 350°C. The lumen degradation, chromaticity shift, and transmittance loss in glass based high-power PC-WLEDs under thermal aging at 150, 250, 350, and 450°C are presented and compared with the silicone based high-power PC-WLEDs under thermal aging at 150 and 250°C. The result clearly indicated that the glass based PC-WLEDs exhibited better thermal stability in lumen degradation, chromaticity shift, and transmittance loss than the silicone based PC-WLEDs. The advantages of glass doped encapsulation in high temperature PC-WLEDs could be arisen from the material property of glass transition temperature 567°C higher than silicone of 150°C. These newly developed high-temperature glass based PC-WLEDs are essentially critical to the application of LED modules in the area where the high-power, high-temperature, and absolute reliability are required for use in the next-generation solid-state lighting.