Abstract: Thiosemicarbazide, phosphoric acid and aldoxime derivatives of chitosan were synthesized and their ability for metal ion adsorptions was discussed. Thiosemicarbazide derivative, synthesized by treating chlorodeoxychitosan with ammonium thiocyanate followed by treatment with hydrazine, was considered to have crosslinked network structure. Phosphoric acid derivative containing both N-phosphonic acid and phosphoric acid groups was synthesized by cyanoethylation of chitosan using acrylonitrile, followed by treatment with hydroxylamine. These derivatives were found to adsorb efficiently infinitesimal concentration (ppb order) of uranyl ion in seawater. Stability constant of some metal ion chitosan chelates were determined. To improve the selectivity in the adsorption of metal ions, a novel method utilizing metal ion as a template was adopted, and the results are discussed.