Controlling the process of crystal growth is of importance to the biomineralization and materials science. In this work, some novel morphology of calcium carbonate (CaCO3) was precipitated in an ethanol-water binary solvent (EWBS) with a CaCl2/Na2CO3 reaction system. For the solutions of CaCl2/Na2CO3 in EWBS, the alcoholization and hydration of Ca2+ and CO32- were discussed from the radial distribution functions by molecular dynamics simulations, and the number density profiles of water molecules around and similar to 15 angstrom away from CO32- were employed to reveal the distribution of water molecules. It is found that EWBS has a divisive effect on Ca2+ and CO32-, and the local inhomogeneity of EWBS would be enhanced by adding some Na2CO3 into it. This inhomogeneity results in an aqueous two-phase system as x(E) goes up to 0.7. In addition, the novel morphology of CaCO3 under different molar ratios of Ca2+/CO32- and in different mixed solvents were confirmed by XRD and SEM, and the relationships between the morphology of CaCO3 and the structural properties of mixed solvents were further explored.