In this work, sheaf-like barium carbonate (BaCO3) crystals were fabricated under the regulation of carboxymethyl cellulose (CMC) via a novel carbonation route with compressed CO2. It was found that sheaves lied in the middle while the rods branched off at both ends of the sheaf. In addition, it was interesting to discover that the fine structures of the sheaf-like BaCO3 crystals (such as the length, sheaf, rod diameter, open-angle, etc.) depended a lot on the concentration of added CMC. As revealed by molecular dynamic simulation, the morphological variations were due to the selective attachment of CMC chains onto (222) plane of witherite unit. The attached CMC chains would change the crystallization manner of BaCO3 crystals and lead to the modulation of crystal morphology. And the growth of sheaf-like BaCO3 crystals were believed to follow twinning and spherulitic growth route. (C) 2012 Elsevier B.V. All rights reserved.