Abstract: The 3-D nonisothermal flow field of polypropylene melt in two non-return injection screws was simulated in plasticizing and injecting phase by using the CFD package Polyflow.The field of temperature,shear rate,viscosity and viscosity heating of melt in two phases were analyzed in this paper.Simulation results indicate that the temperature of melt in the zone of 35° cone screw head is higher than that of 60° cone in plasticizing phase.The temperature and viscosity of melt in 35° cone screw is more even at the exit in injecting phase.35° cone screw is better in injection,since the 35° cone screw matches the barrel better.Compared the nonisothermal flow field with the isothermal one in the zone of 60° cone,the average melt viscosity in some section decreased 24%.The temperature influences all melt physical parameters in the flow field.The nonisothermal flow field is close to the fact.