Disk-like, rod-like, spindle and bundle-like CaCO3 particles were modulated in N-[(2-hydroxyl)-propyl-3-trimethylammonium] chitosan chloride (HTCC) solutions using a slow vapor diffusion method. The CaCO3 particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermogravimetry analysis (TGA) methods. The influences of various concentrations of HTCC, Ca2+ and Mg2+, temperature and aging time, on the properties of CaCbO3 particles were investigated. It was found that the electrostatic interaction between HTCC and Ca2+, the intramolecular and intermolecular interactions between HTCC molecules played a key role in the crystallization of CaCO3 with different morphologies and polymorphs. Based on the analysis of CaCO3 particles obtained under different aging time, a mechanism of HTCC modulating CaCO3 crystallization was proposed. (C) 2016 Elsevier B.V. All rights reserved.