The invention discloses a method for realizing continuous dry breathing of a transformer. The method comprises connecting two filtration drying chambers and one air flow switch, each filtration drying chamber consisting of an upper and lower end cover and a case; arranging a drier layer in the inner cavity of the case; arranging a sintered metal mesh at the air inlet and the air outlet of the lower end cover; arranging an air outlet pipe on the upper end cover; respectively communicating air inlet passages and the air outlet passages of the two filtration drying chambers with the inner cavity of the air flow switch; arranging a solenoid valve in the inner cavity of the air flow switch; fixedly connecting the upper end of the air flow switch with an expansion tank of the transformer; arranging a hygrometer in each filtration drying chamber; and a controller controlling the solenoid valve to switch the air flow according to the humidity displayed on the hygrometer so as to make the two filtration drying tank operate alternately. According to the method provided by the invention, the two filtration drying tanks can be controlled by the solenoid valve to operate alternately so as to continuously absorb moisture and dry the breathing air of the expansion tank, and the controller is adopted to realize automatic control, thereby improving the work efficiency and saving the labor cost.