FEM simulation of aluminum profiles in porthole die extrusion process using Lagrange mesh description will inevitably bring mesh self-contact, severe grid distortion and frequent remeshing, which will result in the loss of computational accuracy and excessive calculation time. In order to solve the above mentioned problems, numerical simulation of aluminum profiles with large and complicated cross-section in extrusion process was achieved using finite volume method based on Euler mesh description. The metal flow behavior and welding course was investigated in detail, which can provide the theoretical guide for porthole die design and optimization. In addition, extrusion experiment was carried out by numerical simulation results. The experimental extrudate was in good agreement with the simulation results, which laid a good solid foundation for non-steady state extrusion process analysis of large scale and complicated cross-section profiles.