Abstract: A novel water-assisted c。一injection molding technology was developed，a three-dimensional，unsteady, non-isothermal theoretical model was formulated using volume weighted average ideas. Based on the model，finite clement numerical simulation was carried out to explore the effect of injection temperature on the process of water-assisted co-injection molding. It showed that the core melt pcnctrating depth and width were not affected by water injection temperature. However, the water penetrating depth increased with increasing water injection temperature. The effecting mechanism was discussed based on rhcological theories.

Key words: water-assisted co-injection molding, numerical simulation, mechanism