The current book describes and apply system dynamics models in economic analysis. Two applications are used, in macroeconomic analysis and in assessment of dams power generation potentials. In the real world, the theories face many obstacles in its analyses and interpretations. One of these problems is overlapping relationships between specific variables and difficulty of determining perfect formulation which contain all possible effect. Traditional statistics tools like regression models try to solve this problem in general case, but it's not enough to give us more information about structure of the system . There are interactions between variables, feedback information, state of the system and variables behavior through time and effect of exogenous variables. One of the most important modern method depend on stock and flow diagram, causal loop diagram and simulation programming, is Dynamics models. dynamics model help us to determine the behavior of the accumulation variables through the time (Population, Cultivable Area, Cultivated Area, Expectation of Oil Reserve, Reserve of LPG, Expectation of Natural Gas Reserve, Total Saving, Emplacement, Capital and DEBT) these make many scenarios to solve the problems now and in the future. In the second application an assessment of the potentials to produce power and reserve water for agriculture of one Sudanese dams.