In this study, numerical simulations of annular extrudate swell of high density polyethylene (HDPE) were carried out. Some important viscoelastic models, such as the Larson, the PTT and the K-BKZ model, were employed for the swell calculation through various types of dies. These numerical results were compared with the experimental ones. The numerical results of the swell. behaviors were very different in each viscoelastic model, while their simple shear flow characteristics were almost the same. As a result, the uniaxial elongational viscosity for large deformation as the steady state region is not important, but the property for relatively small deformation has remarkable effects on the numerical results for the die that have a uniaxial contraction region. Both reversible and irreversible types were tried for the Larson model. It was found that there was a difference between the irreversibility assumption of the K-BKZ model and the Larson model. While there was a serious difference in the response for reversing strain among these viscoelastic models, the response was very important to predict annular extudate swell behavior.