Rheological properties of the composites formed by filling the high-density-polyethylene (HDPE) with carbon black (CB) as well as the irradiation effects were investigated with advanced rheology expand system (ARES). It was found that under the irradiation dose of 40 kGy, HDPE network formed by radiation-induced cross-linking of HDPE molecules. As a result, storage modulus (,G,′) plateau appears at low frequency and loss factor (tg ,δ,) decreases significantly over the entire frequency region. The rheological properties of 25 phr CB composite as a function of the irradiation dose were also explored. It has been demonstrated that at low irradiation dose, cross-linking behavior of HDPE molecules is dominant. At a dose of 100 kGy, an abnormal behavior of storage modulus and loss factor are observed, which can be attributed to the degradation of polymers proved by the gel test.