Individual investors compared major investors have fewer features to decision-making in stock exchange. This factor with unstable and economic and political swings, faced stock exchange to secondary risk of individualism and undetectable behavior of investors that these require to establish a risk management system for optimum stability and stock market development. The target of this research is investors understanding of risk factors and psychological effects. The result show that policies related to the stock market, excessive speculation, disclosure of the information published by companies, information asymmetry, has an impact on risk perception of individual investors, also risk perception has an impact on willingness to re- invest and investment satisfaction. Finally, it can be said that the perception of risk perform a fundamental role in the mechanism of behavioral psychology investors.