A permanent magnet coupling device for a cylindrical transmission shaft comprises at least a group of outer rotor drum assemblies and a group of inner rotor drum assemblies, at least a pair of outer rotor drum shaft coupling mechanisms adaptive to the outer rotor drums, at least a pair of inner rotor drum shaft coupling mechanisms adaptive to the inner rotor drums and corresponding input shaft couplings and output shaft couplings, wherein each group of outer rotor drum assemblies and each group of inner rotor drum assemblies are nested with each other and coupled by permanent magnet air gap magnetic fields; at least radial air gap magnetic field permanent magnet coupling assemblies or axial air gap magnetic field permanent magnet coupling assemblies are arranged and assembled on the adjacent corresponding positions of the outer rotor drums and the inner rotor drums; and the outer rotor drums and the inner rotor drums are coupled with the corresponding input shaft couplings or output shaft couplings by the corresponding adaptive rotor drum coupling mechanisms. The device has the characteristics of higher transmission efficiency, simple and reliable structure, convenient installation, resistance to severe environment, tolerance for shaft eccentricity, load isolation, reduction of vibration and noises, prolonging of equipment life, etc, and has the advantages of not damaging the motors and not affecting the safety of power grids.