The selective polymorph synthesis of aragonite, vaterite and calcite was done by changing the conformation of chitosan molecules. Aragonite crystals in hexagonal prism-like shape were obtained in chitosan precipitates, vaterite crystals in hexagonal symmetrical plate- like shape were prepared in chitosan gel, and calcite nanoparticles were obtained in chitosan sol. The phenomenon of polymorph selection of biominerals by the morphology of biomacromolecules indicates that the studies on the relation between biominerals and biomacromelecules have general interest not only in bionics, but also in biometrics and related fields.