The disclosure uses the Carter's coefficient to correct the equivalent electromagnetic air gap length. And the specific permeance on both sides of the primary core is obtained. Then, the permeance on both sides based on the structure of the primary core is calculated. An equation is established by using the continuity principle of flux, thereby obtaining the air gap magnetomotive force model of current-carrying conductor. The slot vector diagram of magnetomotive force in short primary linear machine is illustrated according to that in the rotating machine. Then, based on the winding arrangement and vector combination, the amplitude and phase of various spatial harmonic wave of the three-phase winding are obtained. Finally, the characteristics of average component distribution of the current-carrying conductor are adopted to obtain the pulsating magnetomotive force generated by the three-phase winding of the linear machine.