The invention relates to an on-line regeneration main transformer respirator provided with a photovoltaic transition and cellular structure heating device and a use method thereof. The respirator comprises a breathing tube which is arranged on an oil conservator and used for absorbing air, the lower end of the breathing tube is communicated with a moisture absorption pot, the moisture absorption pot comprises a pot body, multiple regular-hexagon-shaped honeycomb compartments are formed inside the pot body, each compartment is filled with moisture absorption agents, and each compartment is defined by multiple electric heating panels which are arranged longitudinally. According to the respirator and the method, the on-line heating, drying and regeneration are utilized, and the problems that in traditional main transformer breathing devices, when moisture absorption agents are saturated with moisture and lose efficacy, the moisture absorption agents need to be replaced manually, and in the process of replacement, exit from main transformer heavy gas protection devices is required so that serious potential safety hazards exist are solved, so that the safe operation of a main transformer is powerfully guaranteed, and meanwhile waste of manpower, waste of material resources and environmental pollution in the process for replacing the moisture absorption agents of traditional main transformer respirators are avoided. The regular-hexagon-shaped honeycomb compartment heating device structure is designed by referring to the most reasonable, efficient and material-saving regular-hexagon-shaped honeycomb structure in nature which is fabricated by bees and used for storing honey, and therefore the respirator and the method have the great advantages that the good heating efficiency is achieved, and materials and energy consumption are saved.