Comprehensive evaluations of soil and water conservation may provide principles and a theoretical basis for the policy development of soil and water conservation and the feasibility assessment of technological scheme. An index system was built based on the two factors of the basic situation of soil and water loss and the protective efficiency of soil and water conservation. An evaluation model was constructed based on factor weighted sum, and the factor weights were determined by using AHP and entropy weight method. By taking the typical power transmission projects in Jiangsu Province for examples and using the evaluation model, the study made a comprehensive evaluation of the soil and water conservation benefits and a comparative analysis of the soil and water conservation benefits for different types of soil and water conservation areas. Results showed that, as for the soil and water conservation benefits in power transmission engineering projects, the hilly area had the greatest beneficial result, followed by the general plains area and the sandy plain area. For the fluctuation of soil and water conservation benefits, the general plain area was the first, the hilly area was the second, and the sandy plain area was the third in a descending order.