Abstract: Recently the attitude to dam has significant been changed, man never pursues the short-term benefit of dam but pays more attention to the ecological problem caused by dam project. Aiming at the current understandings towards the social and environment problems caused by the dam construction in the worldwide and the external fact that the policies for dam have been changed in many nations, this article analyzes the status of dam constructing, presents the concept model of advantages and disadvantages relations between the water conservancy resources developing and eco-environment protection, establishes an advantages and disadvantages relation index model for the dam construction project(α=√|A|²+|B|²/EC) and the coefficient model for compensation advantages and disadvantages(P=√|EC|²+|A|²/EC), demonstrates the feasibility of the dam construction according to the analysis of advantages and disadvantages of dam projects. When disadvantages excess advantages, the dam isn't feasible. The compensation of loss what the dam produces must be added in order to maintain the feasibility of dam that is to say to turn its exterior cost into its interior cost. The ration method is dynamic and it essentially embodies the sustainable development. This article selects a certain dam for instance to analyze the advantage and disadvantages relation. The result is disadvantages excess advantages and 8.55623 billion yuan must be compensated in order to maintain the feasibility of the dam construction. At last, this article points out that the opposite relation between developing and protecting could transform according to the sufficient compensation for the eco-environment loss in dam construction.