The sodium lignosulphonate, a natural polymer prepared from alkaline papermaking black liquor through concentration, filtration and spray drying, has good physical and chemical properties such as cohesiveness, dilution, dispersibility, adsorptivity, permeability, surface activity, chemical activity, bioactivity and so on. This product is the dark brown free-flowing powder, soluble in water, chemical property stability, long-term sealed storage without decomposition.