Assessing the benefits of soil and water conservation aims at promoting conservation technology and providing a decision-making basis for eco-construction. Tracing technique by environmental radionuclide can directly determine the net soil erosion within a certain period, and provide information on soil erosion and sedimentation and thire distribution. Therefore, it is a good way for soil erosion assessment. This study tries to use ¹³⁷Cs, ²¹⁰Pb and ⁷Be to trace soil erosion at different time scales, and proposes corresponding calculating formulas.