Although the Urmia Lake is the largest domestic lake in Iran, the second largest saline lake in the world, and the world's 20th largest lake, and is weather-balanced for the region's climate, it has been declining in recent decades. There are several reasons to become dry this lake. In this paper, due to the complexity of the problem, system dynamics is used as a suitable methodology for modeling the reasons for drying Urmia Lake. According to Sterman's methodology, the boundary of the problem was first studied. Key variables and their historical behavior were studied at this stage. Then, the dynamic hypothesis of the problem was formulated by using the subsystem diagram, circular causal graphs, and accumulation flow map. After simulating and testing the model, some of the possible ways were evaluated that lake can be recovery. Based on the results of this study, it seems that two main factors in decrease lake water are reducing the input of surface waters to the lake and damping. Therefore, supplying the Lake right of water and limiting the construction of dams can be two ways to stop the process of drying Urmia Lake. However, the dynamics within the problem, they can apply any solution with many complications and side effects.