Low-density polyethylene (LDPE) was filled with blends of different proportions of two sizes of calcium carbonate (CaCO 3 ; 600 and 2500 mesh). The torque of the LDPE/CaCO 3 samples was measured with a torque rheometer. The results showed that the process torque values of the LDPE/CaCO 3 samples obviously decreased when LDPE was filled with a blend of two sizes of CaCO 3 (600-and 2500-mesh CaCO 3 blend) in comparison with samples filled with CaCO 3 of a single size (600 or 2500 mesh). When the ratio of 600-mesh CaCO 3 to the total CaCO 3 was in the range of 40-60 wt %, the lowest torque value of the LDPE/CaCO 3 samples was achieved. When the content of CaCO 3 in a sample was 30 wt %, LDPE filled with CaCO 3 of different size distributions showed the largest decrease in the torque ratio in comparison with the samples filled with CaCO 3 of a single size. The torques of LDPE samples filled with CaCO 3 of a single size and those filled with CaCO 3 of different size distributions at different temperatures were also studied. The results showed that the flow activation energy and flow activation entropy of LDPE samples filled with CaCO 3 of different size distributions increased obviously. The increase in the flow activation entropy was used to explain the phenomenon of the process torque decreasing for LDPE samples filled with CaCO 3 of different size distributions.