Equal channel angular extrusion (ECAE) is a novel polymer processing technique to produce materials with modified mechanical properties via severe plastic deformation. In this study, at view of optimization for poly(lactic acid), the influence of material nonlinearity characteristics, friction, die geometry within plastic deformation zone (PDZ) and multi-pass extrusion are systematically analyzed by two-dimensional finite element modeling (FEM). Detailed FEM analysis results of stress-strain distribution were then carried out. Results show that equivalent plastic strain increases with die angle at first and then decreases from 0 to 180, and the case at 90 reveals an enough plastic deformation for PLA and more homogeneous deformation in steady stage. The influence of outer corner angle has a higher impact on strain distribution than inner corner angle. By considering friction in model, ECAE tends to perform more realistic resulting in the strain peak shifting to inside. Finally the FEM result of multi-pass extrusion shows that second pass in the same direction provides a more homogeneous deformation than the inverse one. The strong connection between analytical modeling and actual ECAE processing can provide a good guidance for real engineering applications.