The microwave-assisted extraction was used to extract the Rehmannia Root polysaccharides. The extraction conditions were optimized by orthogonal test and the optimal solid-liquid ratio, extraction temperature, microwave power and extraction time were 1:40, 70 ℃, 500 W and 60 s, respectively. Under the optimal conditions, high content of the extracted polysaccharides, determined by Phenol-sulfuric acid spectrophotometry method, was achieved.