The material undergoes the different deformation stage and the changing history of strain-rate and temperature affects the microstructure evolution during extrusion process. To understand the effect of extrusion process on microstructure evolution, the microstructures of aluminum profile with different wall thickness sections are compared and the variety of strain-rate and temperature are analyzed. The result show that the larger increasing gradient of strain-rate leads to the incomplete recrystallization process in thin wall section during the pocket die stage. The coarse grains are developed by second recrystallization because of the violent strain-rate changes, which is caused by the entrance of bearing-land. The lasting time of high strain-rate and temperature decided the growth of coarse grains, which is affected by bearing-land length.