For general lighting, people need more white light. In 1998 the white LED development success. This kind of LED is a GaN chip and yttrium aluminum garnet (YAG) package together. The GaN chip emits blue light (λp = 465 nm, Wd = 30 nm). The Ce3 + -containing YAG phosphor produced by high-temperature sintering emits yellow light with a peak of 550 nm after being excited by the blue light. The blue LED substrate is mounted in a bowl-shaped reflective cavity, covered with a thin layer of YAG mixed resin, about 200-500 nm. The blue light emitted by the LED substrate is absorbed by the phosphor, and the other part of the blue light is mixed with the yellow light emitted by the phosphor to obtain white light. For the InGaN / YAG white LED, by changing the chemical composition of the YAG phosphor and adjusting the thickness of the phosphor layer, white light with a color temperature of 3500 to 10000K can be obtained. This method of obtaining white light by a blue LED has the advantages of simple structure, low cost, high maturity of technology, and thus most applications.