The invention relates to a character input device based on eye tracking and P300 electrical potential of the brain electricity, which comprises a video camera array, an eye tracking module, a keyboard module, a brain electricity signal analyzing module and a system control module. The device combines the high spatial resolution of the eye tracking and the high time resolution of the P300 electrical potential detection of the brain electricity, firstly, determines an area where the keyboard is according to visual lines of a user, and then controls random flickers of all character keys in the area, arouses the P300 electrical potential of the brain electricity of the user, determines the character keys which the user wants to select according to the generation time of the electrical potential and the visual line location, thus realizing the input operation of characters. The invention provides a new human-machine interaction technique which does not need manpower to be involved and is not affected by the noise of the environment for use.