[en] The design of superconducting poloidal magnets was restudied concerning safety. The magnetmotive force of the superconducting air core transformer was reduced from 60 MAT to 48 MAT by shortening the operation period of reactor, so that the maximum repeated tensile stress of structural material (304SS) caused by electromagnetic force was lowered to the level of 24 kg/mm² and stability margin of the superconductor was increased. The deterioration of thermal insulation in the vacuum jacket was studied, and safety valves were designed to cope with it. For repair, dissasembling the poloidal magnet was also studied in relation of the toroidal magnet. Analysis of general failure of the superconducting poloidal magnet was made by event tree and fault tree techniques. (author)