Solution treatment was conducted on Mg-(4-x)Nd-xGd-0.3Sr-0.2Zn-0.4Zr(mass fractuon, %, x=0, 1, 3). The microstructures and phases were studied using scanning electron microscope (SEM), energy dispersive spectrometer and X-ray diffraction. The corrosion rates of the alloys in simulated body fluid were evaluated by mass loss and hydrogen evolution tests, and the corrosion morphologies of the alloys were observed by SEM. It is found that the grain size of the alloy with 1%Gd addition is the finest, as well as the lowest corrosion rate, and the second phase was located relatively continuously around the matrix. While the grain size of the alloy with 3%Gd addition is the coarsest and the corrosion rate is the highest. The alloys exhibit relatively uniform corrosion morphologies, and thus, they are desirable biodegradable materials.