The invention discloses a method and a system, for example, a contact plate, which are used for checking the position of a ray launcher. The ray launcher is a contact pin, a pen, and a needle which can carry on the active-ray launch or a scattering, a reflecting and a diffusing unit which can carry on the inactive-ray launch, such as a pen/needle or a finger of an operator. The ray is modulated and supplied to an at least single dimension detector. The position of the ray launcher is ensured through the output of the detector. The system is used as a standard contact plate, or is used to checkthe position of a launcher, for example a tablet in the wall or the black/white board, or is used in the inner position, for example, a contact plate.