The present disclosure relates to a tank of a high-voltage generator including a tank body and a tank lid. There is an opening in the tank lid. The opening is connected to the bellows so as to counteract the volume change of the transformer oil and avoid generation of bubbles. The tank includes a positive transformer, a negative transformer, a bellows, and other components. The high-voltage winding is embedded in the PCBs. The outer insulating bushing is covered by the PCBs so as to improve the insulativity between the turns of the high-voltage winding. In addition, oil barriers may be placed between the positive and the negative transformers, or between the transformers and the ground so as to eliminate the bridge breakdown effect and make the electric field uniform. By means of said measures, the present disclosure improves the stability of the high-voltage generator.