The impact of different power transmission projects on the environment of the atmosphere, water , noise, etc. It is important to evaluate environmental benefits scientifically and objectively. Evaluate results is for ensuring long-term stability of power transmission projects. This paper puts forward the screening method and decision analysis about the influencing factors of environmental benefits of power transmission project though the analytic hierarchy process (AHP). This paper constructs the index system of environmental impact of power transmission project. We get the weight of environmental benefits about different indicators of power transmission projects, through the surveys. Then we construct the environmental benefit evaluation model of power transmission projects. And we decide the factors which has a greater impacts on environmental benefits. At last we raise the corresponding policy to solute the environmental problems, which arise from the future power transmission projects’ construction.