Considering the basic role of the stator magnetic field (MF), this paper presents a synthesis strategy for stator MF of a permanent magnet spherical motor (PMSM). Given the structure of the PMSM, the MF of a stator coil group with unit current is obtained, and the spherical harmonic components are decomposed, so the relationship between the whole stator MF and coils currents can be deduced by the rotary transformation and superposition. Referring to the rotor MF, the expected stator MF is determined; then, the stator coil currents are calculated by solving a constrained optimization. Finally, the current excitation strategy of stator coils is verified by finite-element analysis and experiments.