A new bi-supported Ziegler-Natta catalyst was prepared successfully by supporting TiCl4 on the carbon black (CB) and magnesium dichloride. Then, this catalyst was used to prepare ultrahigh molecular weight polyethylene (UHMWPE) nanocomposites via in situ polymerization. The effects of difference molar ratios of triisobutylaluminum as activator to TiCl4, polymerization temperature, pressure of monomer and polymerization time on productivity of the catalyst were studied. The maximum activity was obtained at [Al]/[Ti] = 121:1. Increasing monomer pressure raised catalyst activity. Increasing temperature to 60 A degrees C increased the polymerization yield; however, the higher temperature decreased the productivity of the catalyst. Scanning electron microscopic images showed that homogeneous dispersion of CB nanoparticles in the polymeric matrix was achieved without any agglomeration of CB. The crystallization behavior was evaluated using differential scanning calorimeter. The results showed that the crystallinity degree of UHMWPE slightly increased with increasing of CB, indicating that the CB acted as hindrance and nucleating agent. Furthermore, with introducing CB to polymeric matrix up to 1.6 wt%, the melting temperature and crystallization temperatures were slightly increased. The thermogravimetric analysis showed that incorporation of CB has improved thermal stability of polymeric matrix compared to pure UHMWPE. Viscoelastic properties were also investigated using dynamic mechanical thermal analysis. Obtained results showed that with introducing CB, the storage and loss modulus were improved especially at low temperatures and the glass transition temperature was slightly altered. Significant incensement in mechanical properties of the polyethylene was observed by adding nanofiller, in the other words, the presence of CB considerably improved tensile strength, Young's modulus, and yield stress.