Decision making is a hard and long process in portfolio management like any other complex real life problems. Reason of this is the difficulty of selection the portfolio fitting the decision makers criteria from using the great amount of complex data to satisfy investor's goals. Decision Support Systems (DSS) are one of the the efficient methods for the decision makers in order to solve this kind of problems. In this study, a DSS is developed for constituting the portfolios having cardinality constraints. In the model phase of the DSS, Genetic Algorithm (GA) and technical indicator are used. Finally, scenarios are obtained for the purpose of helping investor's decisions.