Two kinds of different size distribution calcium carbonate (CaCO3) particles were blended and filled into ultra‐high molecular weight polyethylene (UHMWPE). The torque of UHMWPE/CaCO3 samples was measured with Haake torque rheometer. The results showed that the process torque of UHMWPE/CaCO3 samples was decreased by filling two different size CaCO3 particles (600 and 2500 mesh) into UHMWPE, compared with the samples filled with single size CaCO3 particles (600 or 2500 mesh). When the content of CaCO3 in the sample reaches 30 wt%, UHMWPE filled with different size distribution CaCO3 particles showed the largest decrease in torque compared with the samples filled with single size CaCO3 particles. We also studied the torque of UHMWPE samples at different temperatures. The results showed that flow activation energy and flow activation entropy of UHMWPE samples filled with different size distribution CaCO3 particles increase significantly. The result where flow activation entropy increased was used to explain the phenomenon that the process torque decreases when UHMWPE filled with different size distribution CaCO3 particles. POLYM. COMPOS., 36:1807–1812, 2015. © 2014 Society of Plastics Engineers