Osteoporosis is a common chronic disease in middle and old aged.Calcium supplement is one of the commonly used means to treat osteoporosis.The accurate measurement of calcium absorption rate can effectively provide scientific basis for clinical calcium supplement.Forty female SD rats were randomly divided into 2 groups: Osteoporosis is a common chronic disease in middle and old aged. Calcium supplement is one of the commonly used means to treat osteoporosis. The accurate measurement of calcium absorption rate can effectively provide scientific basis for clinical calcium supplement. Forty female SD rats were randomly divided into 2 groups: