1. Introduction White light led street lighting manufacturers is a new generation of solid-state green light source, which has many advantages such as energy saving and environmental protection, small size, high luminous efficiency, stable performance and so on. At present, there are three paths for WLED to achieve white light by PC\/MC: 1) blue LED chip + yellow phosphor; 2) purple LED chip + red + green + blue phosphor; 3) blue LED chip + green LED chip +Red LED chip. Among the three ways to realize white light, the most economical and practical way to achieve industrialization is to coat the blue LED chip with yellow phosphor. The light efficiency of the WLED using this way is as high as 250lm\/W. With the increasingly fierce market competition of lighting terminal products and the worsening and worsening of the heat dissipation environment of lighting fixtures, LED light sources must have better thermal characteristics to meet market demand.The thermal characteristics of LED light sources are usually characterized by the ratio of light output to heat. WLED's light output cold-to-heat ratio, that is, the ratio of the photoelectric parameter (luminous flux) of the LED light source at high temperature to the photoelectric parameter (luminous flux) at room temperature. This index can be used to verify the thermal stability of the LED light source. In WLED light sources, phosphors play a vital role in the realization of white light. Phosphors are generally inorganic luminescent materials with ordered crystal structures. The stability of their physical and chemical properties is related to the following factors: material system, dispersion coefficient, powder-to-glue compatibility, and powder morphology. The influencing factors of the WLED light output heat and cold ratio are related to the WLED device materials, and the fluorescent material is the key material in the aforementioned devices.