Due to lacking the measurement results of magnetic properties under rotational magnetization, the application of nanocrystalline alloys for high-power system energy conservation has been limited. In this paper, a high-frequency rotational magnetic property testing system is first introduced. Base on the testing system, the rotating loci of the vector magnetic flux density B and the vector magnetic field strength H are measured. Finally, the rotational core loss and anisotropy of nanocrystalline alloys are discussed and analyzed.