A MOS P-N junction diode includes a semiconductor substrate, a mask layer, a guard ring, a gate oxide layer, a polysilicon structure, a polysilicon oxide layer, a central conductive layer, ion implantation layer, a channel region, and a metallic sputtering layer. For manufacturing the MOS P-N junction diode, a mask layer is formed on a semiconductor substrate. A gate oxide layer is formed on the semiconductor substrate, and a polysilicon structure is formed on the gate oxide layer, and a polysilicon oxide layer formed on the polysilicon structure. A guard ring, a central conductive layer and a channel region are formed in the semiconductor substrate. An ion implantation layer is formed within the guard ring and the central conductive layer. Afterwards, a metallic sputtering layer is formed, and the mask layer is partially exposed.