Chitosan is widely used in agriculture, chemical industry, medicine, environmental protection and other fields because of its wide sources, natural non-toxic, rich functional groups and strong chemical activity. In this paper, the research work and progress of chitosan and its derivatives in the removal of metal ions in solution were reviewed, focusing on the chelating ability of active groups on chitosan molecular chain to metal ions. The chemical modification methods of functional group replacement and recombination of chitosan monomer and physical modification method of changing the physical morphology of chitosan were introduced. The basic principles, application effects, advantages and disadvantages of crosslinking modification, grafting modification, magnetization modification and molecular imprinting were elaborated in detail. The preparation methods and material properties of chitosan microspheres and chitosan membrane were also introduced. In view of the problems in the preparation and application of chitosan and its derivatives, the research direction of efficient and selective removal of metal ions by flocculation chelation mechanism was proposed.