In order to prepare age hardened aluminum alloy with ultra-fine grain structure, a paralled extrusion process with rotated channel and equal angular was proposed. Then, the die model was built, and the die stress analysis on parallel extrusion die with rotated channel and equal angular was conducted by software Deform-3D. Furthermore, the relationship between tolerance value and extrusion force was obtained, and the stress distribution and the influence of tolerance value on die stress were obtained by tolerance interpolation calculation method. The results show that the small tolerance value leads to a great difference between forming force and extrusion force, and an excessive tolerance value may not improve the calculation accuracy and can increase the calculation complexity. However, the exact tolerance value is the key to obtain die stress after mapping the forming force to the die，and the tolerance value is designed as 1. Thus, the safe load at die edge is set as 50 MPa, and the stress concentration region locates at the transition between rotating channel and straight channel. Finally, the die thickness is designed as 40 mm by the method of linear extrapolation.