The invention relates to an LED packaging structure, comprising a radiating substrate, LED chips distributed on the radiating substrate and a transparent cover sealing the LED chips. A sealed space is formed between the transparent cover and the radiating substrate. The LED packaging structure is characterized in that the radiating substrate has internal radiating passages communicated with the sealed space, the radiating passages and the sealed space are filled with a fluid, and the fluid includes two liquids insoluble to each other, a liquid with high density and a liquid with low density, wherein phosphor is dispersed in the liquid with high density and the liquid encompasses the LED chips. Also disclosed is a forming method of the LED packaging structure. Oxidization of leads and weld spots is prevented, radiating effect of the packaging structure is guaranteed, and light emergence uniformity is optimized.