We investigate the magnetic dipole spontaneous emission in the periodic all-dielectric subwavelength spheres array by the magnetic dyadic Green function, together with Cartesian multipole decomposition approach. We find that magnetic Purcell factor exhibits energies splitting (forming quasi-normal modes) due to strong coupling effect between different part of all-dielectric optical antennas. The period plays an important role in the magnetic Purcell effect, and there is an optimized period for the optical antenna to maximize the magnetic Purcell factor. In addition, the magnetic dipole along the spheres’ dimer axis will significantly couple to the higher order multipolar Mie resonances with magnetic Purcell factor greater than 400. Our work will help to design all-dielectric nanoantennas to manipulate magnetic light emission originating from magnetic-dipole transitions and study the magnetic light–matter interactions in topological photonics.