A light guide key plate includes a light guide plate (1). The light guide plate (1) has a plate body (11) with a plurality of keyholes (12). The plate body (11) is formed with flow passages (13) at one side thereof for communicating with the adjacent keyholes (12). The plate body (11) is also formed with overflow grooves (14) at one side thereof with the flow passages (13), and the overflow grooves (14) are extend inwardly from the edge of the plate body (11) and are communicated with the keyholes (12).