The subject invention relates to a type of super-thin plastic key, comprising a top part and a base part; said top part comprising a top part foundation, a layer of light permeable ink and a layer of light-proof ink; using a plastic film as the top part foundation; on said top part foundation is printed a layer of light permeable ink; on said light permeable ink is printed a layer of light-proof ink to display a letter or figure; said top part foundation printed with the light permeable ink and the light-proof ink is subjected to hot-press process to form a top part with a specified shape; said top part and the base part are again subjected to an extrusion monobloc forming process, to form a light permeable super-thin plastic key; by said configuration to achieve the requirements of light weight, thin, short, and small size for electronic telecommunication products; thus avoiding the weakness of poor adhesion and achieving the purposes of simple production and reduced costs.