GdTe3 is a layered antiferromagnetic (AFM) metal with charge density wave (CDW).We grew monolayer (ML)GdTe3 on graphene/6H-SiC(0001) substrates by molecular beam epitaxy.The electronic and magnetic structures are studied by scanning tunneling microscopy/spectroscopy,quasi-particle interference (QPI) and first-principles calculations.Strong evidence of CDW persisting at the two-dimensional (2D) limit is found.Band dispersions and partially gapped energy bands near the Fermi surface are revealed by the QPI patterns.By density functional theory +U calculations,AFM order with stripe pattern is found to be the magnetic ground state for ML GdTe3.These results provide fundamental understanding and pave the way for further investigation of GdTe3 at the 2D limit.