Abstract: As maintenance free respirators with good economy, high utilization rate, and good safety, they are gradually being adopted by more and more new substation main transformers. This article mainly discusses the traditional main transformer respirator and the main transformer maintenance free respirator, which are introduced in detail from the principles, structures, functions, and other aspects. At the same time, combined with the actual situation of the team, the advantages and disadvantages of maintenance free respirators are elaborated.