Abstract: With the development of modern industry, environmental pollution caused by heavy metal ions such as Pb(Ⅱ) has become a globally recognized issue of concern. Chitosan (CS), a widely available renewable biomass material, exhibits excellent biocompatibility and biodegradability. Its molecular chains contain abundant active groups such as amino (—NH₂) and hydroxyl groups (—OH), enabling its widespread use as a metal adsorbent and chelating agent. CS derivatives, obtained through chemical modification of CS, possess tailored structural features that enhance their efficiency in selective adsorption and recyclability for heavy metal ion removal. This review briefly introduces the structure and properties of CS, focusing on two modification strategies—chemical modification and composite modification. It elaborates on the latest research progress in Pb(Ⅱ) adsorption using cross-linked CS, grafted CS, nanomaterial-modified CS, magnetic material-modified CS, and composite carrier-modified CS. Furthermore, the applications of CS derivatives in wastewater treatment, agriculture, biomedicine, lead detection and food are systematically summarized. Finally, future perspectives on the development of CS -based adsorbents are proposed.