An electromagnetic automatic balancing device based on radial excitation includes a shell, a rotatory ring, a stationary ring, a pair of connecting bearings and a controller. The rotatory ring includes two bilaterally symmetrical outer excitation magnetic rings, two bilaterally symmetrical inner excitation magnetic rings, two bilaterally symmetrical counterweight discs, two bilaterally symmetrical first counterweight blocks, two bilaterally symmetrical second counterweight blocks and a pair of rotatory-ring bearings. The stationary ring includes a stator, two bilaterally symmetrical excitation frameworks and two bilaterally symmetrical coils. The rotatory ring and the stationary ring are installed in the shell and connected through a pair of connecting bearings. The stator is installed in the center of the shell. The excitation frameworks are respectively fixed at both ends of the stator.