In this paper, a new type of AC machine was proposed. There were two sets of windings with different pole numbers on the stator. It eliminates the brushes and slip rings. In this paper, the structure characteristic and working principle of electric brushless excitation synchronous machine were introduced. In view of the coupling capability between the two sets of stator windings of brushless electric excitation machine, this paper carried the research on the effect of pole combinations.Based on the finite element analysis, influence of different excitation side selected on the coupling ability was comparatively studied. The air gap magnetic density of brush less electric excitation synchronous machine was achieved. And the key parameters affecting the coupling capability were analyzed, such as pole arc factor, the ratio of magnetic and non-magnetic and magnetic layer numbers. All the results were investigated to provide the guide for the optimal design.