Aiming at revealing the influence of mold temperature on the temperature field and effective stress field of Mg alloy processed by inverse temperature field equal channel angular pressing (ITF-ECAP), a thermal mechanical coupled finite element analysis model of Mg-1.5Bi (wt.%, B2) alloy ITF-ECAP processing was established. Combined with experimental research, the processing process of B2 alloy at different mold temperatures was analyzed. The results showed that during the ITF-ECAP processing, the temperature of the billet significantly increased at the corner of the mold channel, which facilitated smooth plastic deformation. After severe deformation, the temperature gradually decreased, effectively avoiding coarsening of recrystallized grains. The stress concentration area of the billet is mainly distributed at the corner of the channel and near the mold outlet, and it significantly decreases with the increase of mold temperature. The verification experiment found that when the mold temperature was low (200 ℃), the surface of B2 alloy billet cracked after one pass ITF-ECAP processing, while the surface of B2 alloy could be ITF-ECAP processed for 4 passes without surface cracks when the mold temperature was setted as 300 ℃. Further microstructural characterization revealed that a bimodal grain structure consisting of fine and ultrafine grains was formed in the B2 alloy processed by four-pass ITF-ECAP deformation.