The image method has been used for calculating the three dimensional magnetic field and parameters of the superconducting ac generator. It can represent the actual shape of the coils and take account of the conductor cross-section. The influence of the magnetic and conducting Dounaaries are represented approximately by the images in the boundaries and the influence of either conical or stepped boundaries in the end region is represented by forming images on a conical surface with adjustable coning in association with the boundary condition that lead to the possibility to improve the accuracy of the calculation.