Investigations relevant to the influences of AC support and conditions on the surface structure and composition were not reported previously. The present work synthesized a series of NZVI/AC composites using a liquid phase reduction method at a BH₄^- to Fe²⁺ molar ratio of 2:1, 4:1, 6:1, and 8:1 (designated as NZVI/AC-1, NZVI/AC-2, NZVI/AC-3, and NZVI/AC-4, respectively), which were subsequently characterized by various techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. It was demonstrated that the amorphous NZVI partially doping with Fe₃O₄ was immobilized in NZVI/AC-1 sample. The surface structure of the NZVI/AC samples was divided into three types: needle-like shape, interconnected nanoparticles (～30nm) in or close to the pores of the AC support (self-assembling growth), and uniformly dispersed nanoparticles (20–30nm) on the AC surface plane (individual NZVI nanospheres growth). Based on TEM images, NZVI particles found in or close to the pores of AC support were transformed from a needle-like shape to chain-like nanospheres as the molar ratio of BH₄^- to Fe²⁺ was increased from 2:1 to 8:1. Furthermore, the amount of Fe(OH)₃ in the surface oxides increased along with decline of γ-FeOOH and other iron oxides as the molar ratio of BH₄^- to Fe²⁺ was increased. Meanwhile, Pb(II) removal tests indicated that NZVI/AC-4 sample afforded the highest Pb(II) removal efficiency. In summary, the small particle size and low extent of surface oxidation of AC-supported NZVI particles facilitate the intrinsic reactivity in decontaminations.