There are two types of winding in slotless toroidal type winding axial flux permanent magnet machines, one is fanshaped winding, another is rectangle winding. Considering the effect of winding spatial distribution on open circuit back EMF in slotless axial flux permanent magnet machine, the corresponding analytical formulas of back EMF were derived. In order to calculate the end effect function of air gap magnetic field during calculating air gap magnetic field by analytical method, a virtual equivalent linear machine model was built. For verifying the correctness of the analytical formulas, a comparison of back EMF by analytical and FE methods based on a motor design scheme was carried out, the computing results showed that relative error between them was less than 2.1%, the result met the need of engineering. So, the analytical formulas of back EMF could be used as reference for the researchers who designed AFPM machine.