The X ray emissions from Arq+ (the kinetic energy 150 keV and 1.2 MeV) beams impinging on Au surface are measured. The results show that the about 2 keV minimum-potential energy of Ar11+ and Ar12+ (150 keV) is necessary for exciting Au atoms to emit M-X rays. The kinetic energy threshold for exciting target atomic X ray emission is estimated by the semiclassical approximation theory of binary collision.