Abstarct: The main point of this thesis is assesment of the effect of atmospheric dispersion of radioactive pollutants caused by normal operation and accident scenario of the Armenian nuclear power plant on the people and environment of Iran. The main part of the calculation involves calculating the concentration of radioactive pollutants caused by normal operation and accident scenario of the Armenian nuclear power plant and the dose calculation. Also trajectory calculation was used to study atmospheric conditions. In this thesis, first the concentration of pollutants caused by normal operation of the Armenian nuclear power plant during 2008 in two levels 0 & 1.5 m Agl was examined. The results showed the annual external exposure dose for a representative person is less than ICRP 103 recommended dose limit (1 mSv). Two simulation steps were conducted to study the atmospheric dispersion of radioactive pollutants during the accident scenario of the Armenian nuclear power plant. First, by using the HYSPLIT trajectory model, the path of the radioactive pollutants during a 10 years period was evaluated. Accordingly, nine probable accidents were selected and the concentrations of 131I and 137Cs were calculated for these 9 cases. After selecting the 7 & 8/9/2011 as hypothetical accident days, concentrations of 5 types of radioactive nuclei were calculated and annual external exposure dose calculations were performed. In the event of an accident with the same accident scenario in the Armenian nuclear power plant, the north-western regions of Iran have more radiation than other parts of the country. Pars Abad city is one of Iran regions, where the representative person receives more annual external exposure dose than the north-western part of the country. The external exposure dose for a representative person is less than ICRP 103 recommended dose limit (1 mSv) in case of the accident scenario.