Abstract: The remediation of heavy metal-contaminated groundwater is often hindered by the limited mobility of conventional amendment materials, which restricts the formation of effective in situ reactive zones. Active silica-aluminum materials can not only fix heavy metals, but also migrate effectively in aquifers. To construct reaction zone in situ, an active silica-aluminum material was developed in the laboratory by physicochemical characterization, isothermal adsorption experiment, stability test, and column simulation experiment. In addition, site-scale pilot test and engineering demonstration were carried out in the historical leakage area of groundwater contaminated by Zn and Ni at downstream of the tailings pond of a non-ferrous metal mining area. The results show that the active silica-aluminum has nanoscale pore size and amorphous morphology, with the surface zero charge point of approximately 1.7; the maximum adsorption capacities for Zn and Ni are 94.41, 2.40 mg/g, respectively. The fixation mechanism includes ion exchange and precipitation, and the medium of natural sand does not affect its fixation effect on heavy metals. The active silica-aluminum shows high stability, and the polymerization reaction increases with the decrease of pH and the extension of time, following the liquid-solid two phases migration mechanism. Column experiments show that Zn and Ni concentrations at the outlet rapidly decrease to below detection limits following injection, while treatment capacity increases over time. The hydraulic conductivity of the column initially decreases and then increased, with minimal net change. In-situ reaction zone was constructed by injecting active silica-aluminum to immobilize heavy metals in groundwater of the site. The concentrations of Zn and Ni in the pilot area decrease by more than 80% within 40 d. In engineering demonstration area, the migration and diffusion of active silica-aluminum is significant, and the immobilization effect was remarkable. Zn concentration decreases by more than 92.3% after 5 months, and the Zn concentration remains below the standard value of groundwater III. Injecting active silica-aluminum can effectively construct in-situ reaction zone to remediate groundwater contaminated by heavy metals.