Abstract: A numerical analysis method was used to study the effects of the screw arris cross section shapes on the melting process in the melt conveying section in a PVC wood-plastics single-screw extruder. Several rheological experiments were taken to obtain the material viscosity of PVC wood-plastics. The power law model and an approximate Porto Nix model were employed together to get the viscosity model. Polyflow Polymat module was used to fit experimental data and to obtain the rheological parameters of required material in the numerical analysis. A three-dimensional model was developed with Pro/E and the corresponding mesh file was established by GAMBIT and Polyflow mesh superposition techniques (MST). Then the numerical analysis model was established after determining material parameters and boundary conditions. Based on the simulation results, the effects of screw arris cross section shapes on the flow field in melt conveying section of the PVC wood-plastics single-screw extruder was analyzed.