Prefabricated twinning represents an effective strategy for optimizing the microstructure of extruded forming components and facilitating changes in texture. The study examines the incorporation of [10–12] twins into an AZ31 magnesium alloy billet via cold pre-upsetting deformation before alternating forward extrusion (CUAFE). The experimental results indicate that the initial presence of [10–12] twins is advantageous for the development of [10–10] and [11–20] texture components during the extrusion process. In addition, different DRX mechanisms have different influences on the evolution of basal texture. The CDRX grains tend to preferentially select the [11–20] texture orientation, weakening the [10–10] texture and enhancing the [11–20] texture. However, most DDRX grains deviate significantly from the orientation of their surrounding original grain and do not have a preferred orientation. This is reflected in the mechanical properties of the CUAFE part. The tensile strength is 323.5 MPa, while the elongation is as high as 20.1%.