According to mass balance model and the assumption that before ¹³⁷Cs in plow layer was mixed for a uniform distribution,the surface of cultivated soil would form a surface enrichment layer,a quantitative model was developed to relate the amount of ¹³⁷Cs enrichment from the cultivated soil profile to soil deposition rate.During the construction of the model,the depth of surface enrichment layer,the ¹³⁷Cs depth distribution pattern in enrichment layer,the ¹³⁷Cs decay constant,the ¹³⁷Cs input fraction,the depth of plow layer,and sampling year were considered.Results from the model construction prove that the relationship between the rate of soil deposition and ¹³⁷Cs enrichment is neither linear nor logarithmic.