Ce:YAG single crystal for white light emitting diode (LED) is developed to replace conventional Ce:YAG phosphor powder. The effects of changing the Ce:YAG single crystal thickness and the driving voltage on the emission spectra, color coordinates, luminance, luminous efficacy and color temperature of white LED are investigated. Results show that the color coordinates and intensity ratio of blue and yellow-green light can be improved by adjusting the thickness of Ce:YAG single crystals. With the decrease of Ce:YAG single crystals′ thickness, the luminance, luminous efficacy and color temperature of white LED are increased. Pure white emission can be observed when the thickness of Ce:YAG single crystal is 0.6 mm, and its color coordinates are not varied with the change of driving voltage. All results show that Ce:YAG single crystal is a new material for new white LED devices.