Abstarct: Density functional theory (DFT) is a method to study many body systems. The most important approximations applied in DFT are local density approximation (LDA) and generalized gradient approximation (GGA). These approximations in wide range of cases have been demonstrated acceptable results. In the first chapter of this thesis, we have introduced II-VI semiconductors and diluted magnetic semiconductors (DMSs). In second chapter, DFT and wien2k code have been described. Structural and electronic properties of pure ZnTe were investigated in chapter three. In chapter 4 we investigated structural, electronic and magnetic properties TM-doped ZnTe by GGA.