Taking the fractional-slot permanent magnet synchronous linear motor (FPMSLM) as the research object, the analytical formula of its no-load air-gap magnetic field is deduced by the analytical method and verified by the finite element method. The analytical formula of the no-load air-gap magnetic field under the integral coupling length of the FPMSLM stator and rotor is derived. Taking two fractional-slot permanent magnet synchronous cell motors as examples, the no-load air-gap magnetic field under different relative positions of the stator and rotor is calculated by the analytical method and the finite element method at the same time. The waveforms of two methods match very well, which verifies the validity of the analytical method to calculate no-load air-gap magnetic field of FPMSLM, providing theoretical support for the optimization of no-load air-gap magnetic field of FPMSLM.