The magnetic nano-structured Ba-Al ferrite powders were prepared by high energy ball milling under the conditions of various rotation rates and milling times. The micro structure was characterized by SEM, XRD and TEM, and the magnetic properties were obtained by VSM. As the rotation rate and milling time increased, the size of nano-sized particles gradually decreased. The high energy ball milling for 5 h without relation to the rotation rate drastically reduced the coercivity as a consequence of the formation of nano-sized particle with the amorphous structure. However, the coercivity gradually decreased with increasing the milling time, resulting from the decrease of particle size with maintaining the crystal structure.