Abstract: A field experiment was carried out to investigate the functions of polyacrylic acid salt soil amendments by single and mixed application in improving soil physicochemical properties and the root growth of flue-cured tobacco. To study the effects of different treatments on soil fertility, soil water content, soil bulk density and root index. The results showed that: (1) The treatment of Polyacrylamide plus potassium humate showed the highest content in soil organic matter, available N, available P. The Polyacrylic acid potassium plus potassium humate treatment showed the highest content in available K. (2) The treatment of Polyacrylamide plus potassium humate showed the greatest improvement of water retention capacity and bulk density of soil, with the performance in the increase of soil moisture content of soil and the reduction of density being 20-40 cm > 10-20 cm > 0-10 cm. (3) Soil amendments could increase the root-shoot ratio of the tobacco. Root length, root volume and root dry weight were increased the most significantly with the treatment of Polyacrylamide plus potassium humate. The soil amendments increased the proportion of total root biomass at 20-40 cm in the vertical direction. The treatment of Polyacrylamide plus potassium humate is more effective than others to improve soil physicochemical properties and promote growth of flue-cured tobacco roots in the vertical direction to some extent.