In this paper, we report a simple strategy for fabricating hollow CaCO 3 microspheres. We employed poly (ethylene glycol) (PEG) and sodium dodecyl sulfate (SDS) in one system, as a template for the controlled growth of hollow CaCO 3 microspheres. It suggests that the PEG–SDS complex micelles play a key role in controlling the growth of biominerals. The variation of polymer molecular weight drastically changed the morphology and polymorph of the obtained CaCO 3 . These results also present a facile route to biomimetic inorganic synthesis.