Choosing a Stock portfolio in investment discussions is a difficult and difficult task. Deciding which Stock is in a better position compared to other Stocks and deserves to be selected and placed in one's investment portfolio, and how to allocate capital between these Stocks, is a complex issue. Considering the importance of the issue,The main purpose of this research was to investigate the selection of the portfolio of Stock assets based on the method, risk and return of the Stock market in the Tehran Stock market. This study is post-event in terms of practical and methodological purpose, the data collected annually from 1391 to 1402, which includes twenty active companies in the Iranian Stock market. which was selected using the risk minimization model based on the Markotiz model of the optimal portfolio. The results and analysis show that the selection of the efficient portfolio is based on the efficiency frontier diagram of the latest Stock price of the companies based on yield and risk, for example,Amir Kabir Kashan steel has less risk and more yield than all the items. Pars Industrial Carbon Black is less risky than Fan Avran Petrochemical, Chemical Daro Pars. However, it is less efficient compared to Techno-Avaran petrochemicals, but it is more efficient compared to Dorofos chemical. Khuzestan steel has the highest risk and zero return of all items and should not be chosen. Chador Melo, Khark Petrochemical, Mobarakeh Steel have more risk and very very little return,And should not be chosen.