Recent studies on the electrical switching of tetragonal antiferromagnet (AFM) via Néel spin-orbit torque have paved the way for the economic use of antiferromagnetic materials.The most difficult obstacle that presently limits the application of antiferromagnetic materials in spintronics,especially in memory storage applications,could be the small and fragile magnetoresistance (MR) in the AFM-based nanostructure.In this study,we investigated the spin transports in Mn2Au-based tunnel junctions based on the first-principle scattering theory.Giant MRs more than 1000％ are predicted in some Fe/MgO/Ag/Mn2Au/Ta junctions that are about the same order as that in an MgO-based ferromagnetic tunnel junction with same barrier thickness.The interplay of the spin filtering effect,the quantum well resonant states,and the interracial resonant states could be responsible for the unusual giant and robust MRs observed in these Mn2Au-based junctions.