The high temperature interfacial stability of thermoelectric (TE) elements, which is mainly evaluated by the inter-diffusion and interfacial resistivity at the interface between the barrier layer and the TE material, is one of the key factors determining the service performance and application prospects of TE devices. In this study, a screening method based on high-throughput strategy was employed to further improve the interfacial stability of P-type bismuth telluride TE devices, and Fe was proved the preferred barrier layer material for P-type Bi_0.5Sb_1.5Te₃ (P-BT). Then Fe/P-BT TE elements were prepared by one-step sintering. Evolution of the Fe/P-BT interfacial microstructure during high temperature accelerated aging was systematically studied, and stability of the interfacial resistivity was explored. It is found that during aging, the Fe/P-BT interface is well bonded and the composition of the ternary Fe-Sb-Te diffusion layer remains basically unchanged. The diffusion layer thickness increases linearly with the square root of the aging time and the growth activation energy is 199.6 kJ/mol. The initially low interfacial resistivity of the Fe/P-BT interface increases slowly with the prolonged aging time but remains below 10 μΩ·cm² even after 16 d at 350 ℃. The life prediction based on the interfacial diffusion kinetics indicates that Fe is a suitable barrier layer material for Bi_0.5Sb_1.5Te₃ TE elements.