Based on the life-cycle management concept， an estimation method for life-cycle emission reduction benefits of wind power project is proposed. The interval-number theory is introduced to deal with the uncertainty problems， and an interval-number model is built for life-cycle energy saving and emission reduction benefits of wind power project. The model can solve the disturbance from uncertainty factors and provide reliable decision-making basis for the wind power project. Combined with actual data of construction and operating prediction of a million kilowatts wind farm in Inner Mongolia， a comparative analysis on energy saving and emission reduction benefits is made with a selected 600 MW thermal power project as reference， while the sensitivity analysis on two indices of wind power generation and total investment is given. It is proved that wind power project has better environmental benefits in terms of CO2emission， and the total investment of wind power project has bigger influence on the increase of emission reduction cost while the annual power generation is more sensitive to the emission reduction.