Low molecular weight polyethylenimine (PEI) was used as raw material, modified polyamines containing silica and hydrophobic were prepared by hydrophobic grafting of diglycidyl ether oxypropyl trimethoxy silane (KH560) 1-chlorooctane. The structure and properties of the modified polyamine scale inhibitor were analyzed by ir spectroscopy, the conclusions were drawn: the thermal stability, viscosity, surface tension and solution particle size of the modified products were improved. The modified polyamine scale inhibitor was used to disperse sodium aluminosilicate particles, the particles before and after treatment were characterized by infrared spectroscopy, and the dispersion performance of polyamine scale inhibitor was evaluated and its dispersion mechanism was preliminarily discussed by testing the stability and particle settling of the suspended dispersion solution. When the modified mass ratio was m(PEI(polyethylenimine MW=10000)):m(KH560(with -glycidyl ether oxypropyl trimethoxy silane)):m(1-chlorooctane)= 10:2:0.5, the reaction time was 6 h, and the reaction temperature was 75 ℃, the dispersion performance of the synthesized scale inhibitor was the best. When the mass concentration of scar is 30 g/L, the settlement rate of suspension particles reaches the lowest value of 0.047 /d, the settlement rate decreases to 94.8%, and the dispersion is significantly improved. The modified polyethylenimine has a highly effective effect of scale inhibition in the industrial production of alumina, which can be further replaced by the traditional strong acid scale inhibitor by optimizing the conditions in the factory, so as to reduce the degree of pipeline corrosion and reduce the energy consumption.