The difference in the mechanism of radioresistance, the strategy and the level of the adaptation are determined at Apodemus (Sylvaemus) Uralensis and Clethrionomys Rutilus living on the territory of the East Urals Radioactive Trace with the 90Sr contamination density of 180-450 Ci/km2. The mechanism of radioresistance Apodemus (Sylvaemus) Uralensis is based on the use of lipid reserves in energy provision of the physiological functions, what provided of the growth oxidation metabolism in the mitochondria. Found changes testify in favor of stress-realization mechanism of increase of the level energy homeostasis and, inquest, heightened regime of the functioning cells. As a result there is the cellular disadaptation, marked of decrease nuclear, mitochondrial proteins and process of the cellular regeneration, that put obstacles in tissue adaptation. The opposite focus of the metabolic homeostasis at Clethrionomys Rutilus points to limitation use of the lipid reserves in energy provision of the physiological functions, what provided the suppression oxidation metabolism in the mitochondria. The minimization of the functional activity cellular and subcellular structures compensate the growth of theirs numbers as a result of the level tissue and longtime adaptation. This fact characterizes more safety of the level adaptability at Clethrionomys Rutilus to radiation surroundings.