Abstract: ASP flooding technology is an important tertiary oil recovery technology, but the addition of alkali will cause serious scaling problem in oil wells, which reduces production efficiency and increases cost, and limits its popularization and application. Therefore, according to the characteristics of injection fluid, produced fluid and scale sample in the ASP flooding system, the formation characteristics of mixed scale of calcium and silicon by HPAM, HABS and alkali in ASP flooding system were studied by FTIR, XRD and SEM tests. The results show that when HPAM and HABS are a single system, low concentration of HPAM promotes the formation of peanut-like mixed scale, and with the increase of HPAM concentration, the mixed scale crystalline form transforms to hexahedron-like; low concentration of HABS has almost no effect on the mixed scale crystalline form, while high concentration of HABS promotes the formation of worm-like mixed scale. In ASP flooding system, the formation of spherical mixed scale will be promoted when the alkali concentration is low, and the crystal form of mixed scale will change to hexahedron when the alkali concentration is high.