According to mass balance model and the assumption that ceasium-137 in plowed soils shows a uniform distribution through the plow layer, a quantitative model was developed to relate the amount of caesium-137 loss from the cultivated soil profile to rate of soil erosion. The model shows the facts that the radioactive decay of ¹³⁷Cs, ¹³⁷Cs input fraction, the depth of, plowed layer and sampling year have a great influence upon cultivated soil loss from soil profile. The result of model proves that the relationship between the rate of soil loss and ¹³⁷Cs depletion is neither linear nor logarithmic.