Mg65Cu25-xGd10Agx (x = 0-10) amorphous alloy ribbons with 0.1 mm thickness were prepared by melt spinning. The thermal properties and microstructure development during the annealing of amorphous alloys have been investigated by the combination of differential scanning calorimetry (DSC), SEM with EDS capability, X-ray diffractometry (XRD) and TEM techniques. The XRD result reveals that all these as-quenched Mg65Cu25-xGd10Agx alloy ribbons exhibit broad diffraction patterns of amorphous phase. A clear Tg (glass transition temperature) and supercooled region (about 40 K) were revealed for all Mg65Cu25-xGd10Agx alloy ribbons. In addition, the single stage crystallization of the Mg65Cu25Gd10 alloy was found to change into three stage crystallization when the Ag element was added. In parallel, the glass transition temperature for the Mg65Cu25-xGd10Agx alloys exhibits an increasing trend with Ag content. However, the crystallization temperature Tx and supercooled region present a decreasing trend with Ag content.