Binary ordered eutectic materials which have two separated crystallographic phases with different refractive index can reduce light scattering and possess light guiding properties, which may be used in high spatial resolution imaging detectors. In this work, the ordered eutectics GdAlO3∶Tb3+-Al2O3 with a diameter of 3 mm were grown by micro-pulling-down method according to directionally solidified principle. The internal structure of obtained eutectics was determined by SEM and elemental analysis. It was found that the GdAlO3∶Tb3+ crystal fibers were well aligned in the matrix Al2O3 crystallographic phase and the diameter of GdAlO3∶Tb3+ crystal fibers can be adjusted by pulling-down speed during crystal growth process. The faster the pulling-down speed is, the smaller the crystal fiber becomes. At the same time, the radioluminescence properties of GdAlO3∶Tb3+-Al2O3 eutectic samples were determined. The GdAlO3∶Tb3+ crystal fibers can convert X-rays to green lights and the emitted green lights are transported along the fiber direction by total reflection mode, which can overcome resolution reduction caused by light scattering and have potential application for X-ray detection.