There are air gap and machining difficulty for loose coupled rotating transformer in contactless excitation system (CES). The coupling coefficient is relatively small compare with traditional transformer at the same time. There are several problems in the CES, such as loose coupled rotating transformer works inside the motor with high speed, difficult way to control, primary side and secondary side of loose coupled rotating transformer fix on the motor stator and rotor. In view of the adjacent windings type and coaxial windings type, the topology, simulation and experimental research are given in this paper. Through Ansoft 2D model identified two kinds of topology optimal working air gap is 1 mm. Verify the adjacent windings type topology of magnetic line of force closure degree is better than coaxial windings type. The simulation of Ansoft 3D model with adjacent type verifies the magnetic induction intensity is better than coaxial windings type. The experimental prototype of adjacent optimal type on CES to test the design has good transmission effect. The experimental results verify the rationality of the design of the adjacent windings type topology and accuracy, play a key role in improve the contactless excitation system in the future.