The invention relates to the field of electric power, and discloses a compressed air purification device and a ventilation protection device for a self-cooled enclosed busbar. The compressed air purification device comprises a pressure reducing valve, a filter and a separator; an outlet of the pressure reducing valve is connected with an inlet pipeline of the filter; an outlet of the filter is connected with an inlet pipeline of the separator. According to the compressed air purification device and the ventilation protection device for the self-cooled enclosed busbar, dryness and cleanliness of air in the busbar can be kept, therefore, weak local positive pressure is formed in the busbar, and then external air can be effectively prevented from reversely entering a busbar cavity; in addition, filled gas flows in the enclosed busbar, therefore, heat generated by a conductor can be discharged out of the busbar in time, and the constant temperature of the conductor arranged in the busbar is guaranteed.