Different from conductive filament (CF)-type counterparts, interface-type devices exhibit continuously gradual conductance changes, making them the potential for artificial synapses. In this paper, Mn-doped BiFeO₃ (BFMO) devices with SrRuO₃ and TiN bottom electrodes demonstrate the clear CF rather than the interface barrier type resistance-switching feature due to the high Schottky barrier. Considering the measured electron affinity of 3.52 eV and work function of 4.22 eV in the as-synthesized BFMO film (a weak n-type semiconductor, marked as n⁻), we fabricated a hetero-junction device with the Nb-doped SrTiO₃ (NSTO) bottom electrode (a strong n-type semiconductor, marked as n⁺) exhibiting analog switch characteristics. The n⁻–n⁺ hetero-junction between BFMO and NSTO reverses the operation polarity and leads to a barrier transition-dominated conductive behavior in the BFMO-based memristor. The device shows a large ON/OFF ratio over 1200, favorable stability after 10⁴ s, continual multi-value characteristics, symmetrical long-term potentiation and depression, and synaptic plasticity with about 80 ns time constant. The investigation of resistive switching features, band structure, and synapse performance in this work provides a reference for the application of BiFeO₃ in the field of the memristor.