Syndiotactic polystyrene (sPS)/nano-CaCO3 Composites were prepared on a twin screw extruder for the first time. Differential scanning calorimeter and wide-angle X-ray diffraction were used to investigate the effect of maximum melting temperature (T-max) and the content of nanoCaCO(3) oil the crystal forms and melting behavior of sPS for non-isothermal crystallization. The results indicated that the increasing T-max decreases the crystallization temperature of sPS and facilitates the formation of beta-crystal. The addition of nano-CaCO3 changes the melting behavior and crystal form of melt-crystallized sPS and facilitates the formation of beta-crystal. Tile increase in the content of nano-CaCO3 decreases crystallization temperature of sPS and increases the content of beta-crystal, which was similar to the effect of increasing T-max. Pure beta-crystal in sPS/nano-CaCO3 composites can be obtained at lower melting temperature due to the effect of nano-CaCO3. (c) 2006 Elsevier Ltd. All rights reserved.