As research continues, the control on the polymorph and morphology of calcium carbonate (CaCO3) becomes a hot topic because its application is limited by these parameters. The polymorph and morphology control of CaCO3 was successfully achieved via temperature and PEG (Mw = 6000) during the decomposition of Ca(HCO3)2, which has rarely been employed to prepare precipitated CaCO3. As-prepared CaCO3 was characterized using XRD and SEM. In the case of no PEG, rhombohedra calcite, lamellar vaterite, rod- and needlelike aragonite are observed, and calcite is the major phase at all samples and it increases with temperature, whereas vaterite and aragonite decrease with temperature. The addition of PEG restrains the formation of vaterite and promotes the emergence of needlelike aragonite particles at 70°C, and prevents the generation of calcite and encourages the production of rodlike aragonite particles at 80°C and 90°C. This work not only provides a new way on the preparation of CaCO3 powder but also presents the feasible control method in this route.