Abstract: Extrusion molding is an important method in polymer processing industry. The stress concentration of polymer melt can occur easily at the nearby region of contraction entrance in the process of extrusion molding, which causes volume defects of the final parts. For the purpose to eliminate or reduce the volume defects, the effects of contraction profiles on the rheological behaviors of polymer melt are mainly investigated based on numerical method, including V-shaped and trumpet-shaped contraction profiles at different contraction length. Rolie-Poly model is used to describe the stress-strain relationship of polystyrene melt in 4:1 contraction flow. Numerical simulations of the principal stress difference, the first normal stress difference, stretch ratio and velocity in V-shaped and trumpet-shaped contraction flows are implemented based on finite volume method and SIMPLE algorithm. Numerical results show that the V-shaped, trumpet-shaped contraction profiles and the increase of contraction length can reduce the stress concentration, the trumpet-shaped contraction profiles have better results under the same contraction length compared with V-shaped contraction profiles.