Decision makers uses several quantitative models for the selection of suitable investment alternatives, high yielding and high competitive ones, and what the most needed to the Syrian economy, especially in the reconstruction phase, is to test these models and study their credibility in leading the investment process, and from this point this research is studying the internal rate of return model in the evaluation of investments, which draws the importance and the need for professionals and investment decision-makers reliance on this indicator in their studies and analysis, as well as a range of models of different quantity, in order to obtain top payoff of investment alternatives available to them and to achieve competitiveness for their projects and businesses.