In this paper, calcium carbonate particles with unusual morphologies could be successfully synthesized by a precipitation reaction of sodium carbonate with calcium chloride in the presence of a novel polymer-surfactant aggregate consisting of poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) and sodium dodecyl sulfonate (SDS). The as-prepared products were characterized with scanning electron microscopy and X-ray diffraction. The results showed that the SDS concentrations, the molar ratio of CO32- to Ca2+ (R), and the reactive temperature in the mixed system turned out to be important parameters for control of morphologies of the as-prepared CaCO3 particles. Various unusual crystal morphologies, such as hollow microsphere, cubic, and rombehedra, etc., can be obtained depending on the experimental conditions. Moreover, the formation mechanisms of calcium carbonate with different morphologies were discussed.