Ce:YAG transparent ceramics could be combined with blue LEDs/LDs, for applications of high power white LEDs/LDs. In this study, it is found that by adjusting the thickness of Ce:YAG transparent ceramics and the doping concentration of Ce³⁺, the emission spectra and color coordinates of the assembled devices can be adjusted from the cold white region to the warm white region. (Ce_xY_1-x)₃Al₅O₁₂ (x=0.0005, 0.0010, 0.0030, 0.0050, 0.0070 and 0.0100) transparent ceramics was fabricated by a solid state reaction method, with the high pure (≥99.99%) commercial powdersα-Al₂O₃, Y₂O₃ and CeO₂ using as raw materials. The ceramic green bodies were sintered in 1750 ℃ for 20 h under vacuum of 5.0×10^-5 Pa, and the ceramics were annealed at 1450 ℃ for 10 h in the muffle furnace. The in-line transmittance of double polished Ce:YAG ceramics is higher than 79% at 800 nm (0.2, 0.4, 1.0 mm in thickness, respectively). The thermal conductivity of Ce:YAG transparent ceramics decreases with the increase of measuring temperature and doping concentration. Thermal distribution of ceramics and LEDs with different thicknesses was simulated by the finite element method, and the thermal distributions of three packaging modes were compared. White light with chromaticity coordinates of (0.3319, 0.3827) and (0.3298, 0.3272) and luminous efficiency of 122.4 and 201.5 lm/W were prepared by combining transparent ceramics with LEDs/LDs. We combined Ce:YAG transparent ceramics and blue LEDs chips to produce 10 and 50 W mature lamps, which can be used for commercial purposes. Therefore, the Ce:YAG transparent ceramics is a highly promising color conversion material for high power lighting and displaying applications in the future.