In order to explore the property of white light LED, we build the phosphor model which is encapsulated with different LED wavelength. we use the Monte-Carlo ray tracing method with Mie scattering theory to simulate the scattering behavior in YAG phosphor, and obtain absorption coefficient and transfer efficiency by 2-nd ray tracing. Because the spectrum of blue light will distort by YAG phosphor, we introduced a coefficient β to compensate the distortion of blue light spectrum, and recover the original spectrum by superposition. At last, we verified the accuracy of model by experiment.