Abstract: A process was developed to prepare nanocrystalline and quantum-confined particles of manganese-doped zinc sulfide in chitosan organic film by an ion-coordination method. Chitosan that contains ligand groups acts as not only a polymer matrix but also a surfactant. By the reaction of zinc acetate and manganese acetate mixture in chitosan film with sodium sulfide solution, particles size of 4.0-6.0nm were achieved by controlling the reaction time and manganese was successfully doped. The optical characteristics shown by PLE and PL spectroscopy were discussed. A coordination model of the chitosan film which results in formation of the ZnS: Mn nanoparticle was described.