Abstract: The computational fluid dynamics software POLYFLOW was used to simulate the inflation stage in extrusion blow molding of an HDPE oil drum and calculate the velocity distribution of parsion, the thickness distribution and contact time after inflation. The results show that, the thickness decreases as the blowing pressure increases. The thickness at the bottom and corners of the blown drum is thinner than that at others. The velocity increases as the blowing pressure increases after pinch-off. The parison contacts with the mould earlier as the blowing pressure increases. In the region of the handle, the contact time is the shortest.