Contactless transformer is the key part of the inductive contactless power transfer (ICPT) system. In this paper, a high coupling coefficient contactless transformer is proposed with asymmetric trapezoidal shape cores. With 3D finite element methods (FEM), this paper calculated coupling coefficients of the transformer in different inner lateral side distances and bending angles of the magnetic core and obtained the distribution of magnetic field and the power transmission characteristics. The results indicated that the high coupling coefficient contactless transformer can improve the coupling performance and power transmission efficiency of the ICPT system.