Abstarct: In this thesis, we have studied the electronic and magnetic properties of transition mextals (TM) - doped CdTe by Wien2k code. The generalized gradient approximation (GGA) were used for these calculations. Transition mextal elements such as Cr , Mn , Fe and Co were doped in CdTe with amount of %6.25, %12.5 and %25. The energy and bulk modulus of systems were calculated by volume optimization . The reults showed that all compounds except compounds doped with Mn are stable in ferromagnetic phase. The stable phase for Mn doped CdTe was anti- ferromagnetic. Cr, Fe, Co-doped CdTe for ferromagnetic phase and Mn- doped CdTe for anti-ferromagnetic phase showed semi-mextal properties. Moreover, Cd0.75Cr0.25Te compound has biggest bandgap energy. Investigation of density of states for the system showed that in the conduction band TM-3d orbitals hybrid with Te-5p orbitals. In fact these orbitals have a major contribution in the density of states, near to the Fermi energy.