Altemagnetic materials have recently broken through the spin degeneracy limitation of conventional antiferromagnetic tunnel junctions, offering new opportunities for developing novel spintronic devices. However, maintaining high thermal stability and significant tunneling magnetoresistance (TMR) while utilizing altemagnetic semiconductors to simplify device architecture remains a key challenge for achieving high-density storage devices. This work presents a tunnel junction based on a V₂Se₂O/Fe₂B van der Waals heterostructure. By exploiting the spin-splitting effect in the momentum space of altemagnetic materials, this structure overcomes the inability to achieve TMR in conventional antiferromagnetic tunnel junctions due to spin degeneracy. Simultaneously, the exchange bias effect at the ferromagnetic/altemagnetic interface effectively enhances the thermal stability of the ferromagnetic layer, replacing the conventional synthetic antiferromagnetic pinning layer and significantly simplifying the device architecture. First-principles calculations based on density functional theory combined with non-equilibrium Green's function formalism demonstrate that the V₂Se₂O/Fe₂B heterostructure achieves a TMR of 283% at room temperature, with further optimization potential through material doping or electrostatic gating. This study demonstrates the feasibility and application prospect of altemagnetic materials in next-generation spintronic memory devices, while substantially reducing structural complexity and enhancing thermal stability.