The invention relates to an LED (Light Emitting Diode) horizontal fluid dissipating COB (Chip-On-Board) light source and a packaging process thereof. The COB light source comprises a microarray heat pipe flat plate, a copper plating layer, a silver plating layer, a line layer, an insulation paint layer, a chip and silica gel, wherein the microarray heat pipe flat plate, the copper plating layer, the silver plating layer, the line layer and the insulation paint layer are sequentially compounded; the external surface of the chip is fixed by the silica gel in a sealing manner; the chip is tightly adhered to the silver plating layer and is fixed by welding; the appearance of the microarray heat pipe flat plate is laminated; the microarray heat pipe flat plate is subjected to cold-drawn by using an aluminum product to be integrally formed; a plurality of microarray channels which are operated independently are distributed in parallel inside the microarray heat pipe flat plate; the microarray channels are filled with a working medium; two ends of each microarray channel filled with the working medium are sealed. After the surface of the microarray heat pipe flat plate absorbs heat, the working medium in the microarray channels evaporates, heat is quickly transferred to a condensation section and then is released, and then the working medium returns to an evaporation section to continuously absorb heat, thus a series of continuous phase transition heat and mass transfer processes are repeated.