As the blue and yellow lights are complementary colors, a blue InGaN LED chip is coated by a yellow phosphor film to generate white light based on luminescence conversion mechanism. The emitted light of a blue LED is used as the primary source for exciting fluorescent material such as cerium doped yttrium aluminum garnet with the formula Y3Al5O12∶Ce3+(in short: YAG∶Ce3+). The matching of the spectrum of the blue LED chips and the YAG∶Ce3+yellow phosphor is studied to improve the conversion efficiency. The packaging methods and manufacturing processes for high-power single-chip-white-LEDs are introduced. The uniformity of the output white light is investigated. Based on the characteristics of the high-power white LEDs, some approaches and processes are suggested to improve the light uniformity when they are fabricated. The effectiveness of those approaches on the improvement of LEDs is discussed in detail and some interesting conclusions are also presented.