AbstractA spectrum calculation code including the effects of one spectator electron has been constructed. Assuming that ions with a spectator electron are related with next ionization stage under local-thermal-equilibrium (LTE), the spectator orbitals which are treated in this code are determined by the Griem's boundary. Excited levels higher than the boundary satisfy the LTE condition approximately. In this paper, the effects of a spectator electron on the X-ray spectra from Ar ions are discussed.