Abstract: The singlescrew extruders is simplified as a 3D rectangle cavity. In order to investigate the effect of the screw speed and material elastic property on residence time distribution, the flow field is simulated by means of finite element method (FEM) and particle tracing technology. Meanwhile, the “complete model” is employed to fit the experimental data, and the volume fraction of plug flow, mixing flow and dead region are quantitatively characterized. The results show that the flow pattern in the screw channel is dominated by plug flow while includes CSTR, dead region and their mixture. The flow pattern is affected by the rheological behavior of the materials and operating conditions.