The increase in metal mining, processing, and smelting activities has precipitated a substantial escalation in the contamination of soil by heavy metals. Ferrihydrite (FH) has been commonly used as an amendment for the immobilization of heavy metals in contaminated soil. However, FH suffers from drawbacks such as agglomeration and nonmigratory characteristics, which limit its practical application in soil remediation. Herein, a colloidal ferrihydrite material (FH-SG) was prepared by using organic molecules with multifunctional groups as well as negative charges and combined with ferrihydrite. The results showed that FH-SG with abundant surface hydroxyl groups (-OH) and large specific surface area (91.5 m2/g) can be well suspended, stable at pH 4–12, negatively charged at a wide pH (>4.8). When the FH-SG was added into contaminated soil with the rate of 1:2–1:4 g/mL, the stabilization rates of soil water-soluble As, Pb, and Cd reached 94.66–95.63%, 96.12–98.33%, and 95.52–96.37%, respectively, and the stabilization rates of soil bioavailable As, Pb, and Cd reached 72.22–77.19%, 49.39–52.91%, and 25.30–30.51%, respectively. The maximum migration distance in quartz sand and soil media with different particle sizes can reach 2.07–2.92 m and 0.78–1.08 m, respectively. Altogether, our findings clearly demonstrate that FH-SG exhibits better stabilization and migration than those of FH alone and most proposed FH colloidal systems. The FH-SG colloidal system holds significant promise for the remediation of various kinds of complex polluted soil.