In this thesis, in order to probe into phosphor powder in the optics characteristic of white light LED encapsulation and set up accurate optics model, we combine Monte-Carlo method and volume Mie scattering effect to simulate light transmit in phosphor powder, and record of the space distribution of photon absorbed; it is the new light source that be exciting phosphor, and the optics behavior described the white light LED by blue and yellow two times of light tracing. With the verification of the experiment and simulation, we succeed in setting up the optics model of equivalent YAG phosphor, and apply to the analysis of white light LED encapsulation, can find out the optimization result to the LED encapsulation that is designed by oneself, simulation is analysed all energy happens in it, extract efficiency, and the correlate colour temperature distributed in three-dimensional space.