Abstract:The results of the experiment show that the prepared Rhizomae Rehmanniae can obviously improve the change of weight, quality of drinking water, urine and serum level of T3, T4 and AD of the hyperthyroid Yin deficient rats, and thus administers to the nourishing of Yin. The action of nourishing the kidney Yin is related with improving the serum level of AD in the body.