An analytical calculation method of air gap magnetic field in axially magnetized tubular permanent magnet linear synchronous motor (TPMLSM) based on Schwarz Christoffel (S C) transformation method was introduced. Firstly, the air gap magnetic field distribution of the slotless motor was analytically calculated based on S C transformation method. Then, the air gap relative ratio permeance function of slotted motor was obtained based on S C transformation to consider the effect of stator core slots. Finally, the air gap magnetic field distribution of the slotted motor was obtained by the basic air gap magnetic field of the slotless motor and the air gap relative ratio permeance function. The analytical formulas of the air gap magnetic field distribution were derived for the axially magnetized TPMLSM. Experiment was carried out using a 36 slot 12 pole axially magnetized TPMLSM. The predicted air gap magnetic field distribution matched the corresponding finite element result, and the measured no load electromotive force (EMF) of the prototype was also consistent with the analytical and the finite element value, so the validity of the proposed method was proved.