Polypeptide-based doubly-hydrophilic hybrid copolymers (PEO-b-PPLG-g-MPA) containing a great amount of carboxyl groups at the sidechains of polypeptide blocks were synthesized by combination of ring opening polymerization of  N-carboxyanhydrides (NCAs) and thiol-yne photo-click reaction. The obtained polypeptidebased doublyhydrophilic hybrid copolymers (DHHC) were used as protein template to direct biomineralization of CaCO

3

in aqueous solution. Conformational changes of the polypeptide blocks were revealed by circular dichroism (CD) spectroscopy. Morphology of the obtained CaCO

3

was investigated by scanning electron microscope (SEM). Crystal form of the CaCO

3

was confirmed by x-ray diffraction (XRD). The results of CD analysis indicated that the polypeptide blocks could effectively control the morphology of CaCO

3

in water when they adopted random coil conformation

rather than more ordered α-helix or  β-sheet. SEM analysis showed that the growth of the CaCO

3

crystals was strongly dependent on the concentration of polypeptides. Furthermore

the morphology of CaCO

3

was tunable by the variation of length of polypeptide blocks and pH value of the aqueous solution. CaCO

3

could form the microsphere with smooth surface

spherical superstructures with some tiny disklike particles grown on the surface and “flower” aggregated nanorod structures. XRD analysis verified that the obtained CaCO

3

was calcite in a very stable form in nature.