Abstract: Objective:to study the pathological changes of brain in diabetic rats and to investigate further the relation between intracellular calcium deposits and brain tissue damage.Methods:intracellular calcium deposits in brain of STZ induced-diabetic rats and ischemic diabetic rats were observed by ultrastructural calcium cytochemical method. Results:increased amounts of calcium precipitate were detected in diabetic rat cerebral tissue by electron microscopic observation. The prominent calcium accumulation in ischemic neuron and enlarged glial processes were shown after temporary cerebral ischemia in diabetic rats.Conclusion:The results indicated that change of intracellular calcium in diabetic rat brain may participate in the progress of neuron damage in diabetes and acceleration of ischemic injury by hyperglycemia.