Provided are an electrolyte for a magnesium secondary battery having improved ion conductivity and stability, and a method for preparing the same. The electrolyte for a magnesium secondary battery shows higher ion conductivity as compared to the electrolyte according to the related art, increases the dissociation degree of a magnesium halide electrolyte salt, and provides stable electrochemical characteristics. In addition, after determining the capacity, output characteristics and cycle life of the magnesium secondary battery including the electrolyte, the battery provides significantly higher discharge capacity after 100 cycles, as compared to the electrolyte according to the related art. Therefore, the electrolyte may be useful for an electrolyte solution of a magnesium secondary battery.