By using the mass balances model and by introducing an erosion constant (mean annual relative loss of 137Cs) and depth distribution function of 137Cs in soil, a quantitative model of soil erosion rate using 137 Cs loss was developed for uncultivated soils. Depth distribution patterns of 137Cs in the soil profile, sampling years, and the amount of 137Cs fallout each year were considered. The model shows that the estimated rate of soil erosion is controlled mainly by the distribution pattern of 137Cs in the soil profile. By inputting different depth distribution functions of 137Cs, the year of sampling and the different input fraction of total fallout value each year, several simulation results of soil loss were given. The results of numerical simulation proved that the relationship between the rate of soil loss and 137Cs depletion is neither linear nor logarithmic. They are dependent on the distribution patterns of 137Cs in the soil profile, sampling year, and input fraction of total fallout value.