Abstarct: In this thesis, the structural, electronic, UV-Vis properties as well as the oxidation potential values of pyrrole oligomers including dipyrrole, tripyrrole, tetrapyrrole, pentapyrrole, hexapyrrole, heptapyrrole and octapyrrole were investigated using the quantom mechanical method. For this purpose, the density functional theory method in the B3LYP / 6-31G (d, p) level of theory was used with polarizable continuous model in water and tetrahydrofuran solutions. The results of structural calculations showed that the addition of pyrrole monomers to the oligomeric chain reduces the amount of bond alternating, which is less in the oxidized state with respect to the neutral form. The values of the dihedral angles between the pyrrole rings along the neutral oligomer chain decrease with the addition of the pyrrole monomers so that in the doped state it approaches zero. In the case of solvent effect, the lowest deviation from the planar stucture observed in water, THF and gaseous mediums, respectively. The study of frontier orbitals showed that the energy gap between HOMO and LUMO was reduces greatly in oxidized states relative to the neutral states. This reduction in energy gap continues with the addition of the pyrrole monomer to the oligomer chain.Therefore, th π- electron conjugate was better corres panding to facilitate the charge transfer and the conductivity of these oligomers. In addition, as the length of the oligomeric chain increases, the ionization energy decreases in which facilitates the oxidation process. The results of the simulated UV/Vis spectrum indicate that λmax values increase more in the oxidized state than in the neutral form. The effect of increasing the pyrrole monomer to the oligomeric chain also has the same trend. The predicted oxidation potential values for the studies molecules are in good agreement with their experimental values. In addition, increasing the length of the oligomeric chain causes the reductin of oxidation potential, which is consistent with the results obtained form their electronic properties. The observed trend for oxidation potential of the studied samples showed a very good correlation with ionization energy and the highest occuped molecular orbital.