Mathematical model for prediction of dynamics of 90Sr and 137Cs accumulation by perennial cereal grasses from contrasted by properties soils at the late phase of radiation accident was verified. Results of the model testing has shown the possibility of accountability of the role of processes, which predetermined the dynamics of radionuclides accumulation by plants (90Sr and 137Cs carry-over from root-inhabited soil layer, its immobilization and physical decay). Prediction assessments of 90Sr and 137Cs accumulation by perennial cereal grasses from contrasted by properties soils at the late phase of radiation accident was calculated with the use of realized in the model approaches.