Abstract: Nesquehonite (MgCO₃·3H₂O) whiskers were prepared by thermal decomposition method using magnesium solution as precursor. The influence of pyrolytic time, concentration of magnesium solution and stirring rate on the decomposition process is analyzed. The phase composition and micro morphology of the products was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that smooth rod-like MgCO₃·3H₂O whiskers with an average diameter of 6.0 μm and an average length of 100 μm was obtained at 50 ℃ when the pyrolytic time was 120 min and the concentration of magnesium solution was 2.75~3.39 g/L. With the increase of time and concentration, the surface or the whole rod-like structure of MgCO₃·3H₂O crystal will dissolve to form amorphous particles, and gradually to form porous rod-like 4MgCO₃·Mg(OH)₂·4H₂O. The stirring rate plays a great effect on the yield of MgCO₃·3H₂O whiskers. In MgCO₃·3H₂O crystal, MgO₆ octahedron is tightly connected by Mg-O bond in the form of a common vertex. The long chain is formed by infinite connection along the direction of 010 where the chemical bonding force is strong. The linear fitting results of crystallization kinetics showed that the concentration of magnesium solution increased, the induction time shortened.