The thermoplastic filled with the different size distribution fillers was a new method for improving processability of thermoplastic composites. In our former study, we found that the melt torque of low-density polyethylene (LDPE) composites, which were filled with 30 wt % the effective size distribution CaCO3, evidently decreased. In this article, two sizes of CaCO3, 600 meshes and 2500 meshes, were blended by different proportions and were filled into LDPE matrix with 30 wt %. Crystal process, isothermal crystallization kinetics, and nonisothermal crystallization kinetics of a series of composites were characterized by differential scanning calorimeter (DSC). The results showed that composites filled with the effective size distribution CaCO3 leaded to the lower melting and crystallization temperature, the more wide crystallization temperature area, while their the crystallization rate constant (k) of isothermal crystallization kinetics decreased and their Avrami exponents (n) and crystallization half-life (t(1/2)) of isothermal crystallization kinetics increased compared with those of the composites filled with the single size CaCO3. Nonisothermal crystallization kinetics had the similar results. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 120: 3490-3500, 2011