This paper describes a novel hydrazine hydrate-modified pectin for the removal of Hg²⁺. The modified pectin was characterized by elemental analysis and FT-IR spectroscopy which indicated that hydrazine hydrate was successfully grafted on the side chains of pectin. In addition, the reaction mechanism between modified pectin and Hg²⁺ was studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results revealed that the removal effect was probably due to the form of the coordination bonds between Hg²⁺ and N/O atoms. Under optimized experimental conditions, the efficiency of removal Hg²⁺ by the modified pectin reached 74.8%, which was far higher than the 30.5% obtained with unmodified pectin.