It was shown 137Cs transfer factor (TF) from soil in plant is determined by time of incubation radionuclide in soil t and complex of soil properties Sef and independent from density of soil contamination . Parameters characterising interrelation among main compartments of a "soil - plant" system as TF, period of half decreasing of TF - and constant reflecting changes of a soil properties . These parameters are determined in empirical way for a wide range of ecological conditions and crops including main components of human and animals diet. The proposed method allows to predict 137Cs concentration in main agricultural crops with adequate accuracy for estimate radiation situation after environmental contamination.