The purpose of this paper is to verify the electromagnetic formula of the magnetic torque acting on permanent magnet. The proposed method uses a pendulum motion system to obtain the real measurement and compared to the theoretical calculations. From the angular position measurements of pendulum motion, the magnetic torque in the locus is obtained. The problem of difference amplication of noise in high sampling rate is overcome by B-spline curve fitting method. The errors of the measuring results and theoretical calculation are significant mainly due to the magnetic field being induced by the perme-nant magnet near the iron core of electromagnet. In the paper, the problem to cause errors is analyzed and discussed, and modification to the existing formula is made. The improvement of calculation result is discussed.