Abstarct: In this thesis, the electronic structure and magnetic properties of transition mextal (TM)-doped ZnS semiconductors have been studied by wien2k code. Cr, Mn and Fe were doped in this system . TM doping percent were 6.25% ,12.5% and 25% . In these calculations, we have used the generalized gradient approximation (GGA) and the exact exchange-correlation electron (EECE). The results of this study were exhibited that the lattice constant of the samples decreases as the magnetic ions increases. Comparison of the total energy between the antiferromagnetic (AFM), ferromagnetic (FM) and paramagnetic (PM) states were indicated that the stable phase of Cr and Fe doped- samples is FM while for Mn doped-sample is AFM. Investigation of the total density of states of the doped-samples showed a half mextallic behavior for Cr- and Fe- doped ZnS. The results of the calculation of the band structure for TM-doped samples show that all compounds have direct band gap. The values of the total magnetic moment of the Cr- and Fe- doped ZnS increases as the ionic dopant increases. The total magnetic moment was zero for Mn-doped samples.