The effects of trace Ag on the tensile strength and creep resistance of Mg-7.5Gd-1.5Y- 0.4Zr (wt.%) extrusion bars were investigated at temperatures of 175-275 °C, via tensile tests and creep tests, electron back-scatter diffraction, and transmission electron microscopy. Adding trace Ag improves the tensile strength and creep resistance of Mg-Gd-Y-Zr alloys at elevated temperatures. During the creep process, precipitate-free zones (PFZs) are formed near grain boundaries and perpendicular to the loading direction, while chain-like β′-Mg₇RE precipitates are distributed in a special direction ( ) in grain interior. After adding Ag element, the creep resistance of the Mg-Gd-Y-Zr-Ag is improved due to the suppression of dislocation movement by the synergistic effect of narrower PFZs, finer β′-Mg₇RE precipitates in the grain interior and more stable β-Mg₅RE phase located on the grain boundaries.