A packaging method of an organic light emitting diode (OLED) is described. First, a substrate is provided, and the substrate has the OLED device formed thereon. Thereafter, at least one protection layer is formed on the substrate, so as to cover the peripheral sidewall of the OLED device entirely. The step of forming the protection layer includes forming an organic layer on the substrate, and then forming a metal layer on the organic layer, wherein the metal layer at least covers a sidewall of the OLED device. Afterwards, an oxidation treatment is performed, so as to oxidize a portion of the metal layer.