This paper presents the analytical analysis of magnetic field and back electromotive force (back EMF) calculation in an axial flux permanent magnet synchronous generator (AFPMSG) without stator core. For the verification, the numerical analysis finite element method (FEM) of magnetic field is accomplished and comparison between analytical and numerical solution of magnetic field is presented. Both analytical and numerical solutions are obtained via magnetic vector potential, respectively. This paper also presents the comparison between analytical solution and numerical (FEM) solution of back EMF using Faraday's law. The verifications show that good agreement between analytical and numerical solution of magnetic field and back EMF is obtained. The validity of the proposed analytical method is additionally confirmed with measurements of back EMF on prototype AFPMSG with coreless stator.