Polysaccharides are an important component is human diet.The present study was to characterize the water-soluble polysaccharides isolated from Glycyrrhiza uralensis Fisch grown in Xinjiang of China.Three polysaccharides namely GPS-2a,GPS-3a,GPS-4a were isolated by hot water extraction,ethanol precipitation,DEAE cellulose dialysis and Sephadex G-100 gel filtration.GPS-2a,GPS-3a and GPS-4a were subjected to the structural analysis using infrared spectroscopy (IR) and atomic force microscopy (AMF).In addition,effect of GPS-2a,GPS-3a and GPS-4a on mitogenic activity of mouse spleen lymphocytes and NK cells was investigated.Results of the experiments in this reasearch showed that GPS-2a,GPS-3a and GPS-4a were different in chemical structure and microcosmic appearance.