The invention mainly relates to the electric field, in particular to a full-sealed sampling device and process for mutual inductor insulating oil. According to the full-sealed sampling device for mutual inductor insulating oil, a second injector can perform cleaning, exhausting and quantitative extraction on insulating oil samples very conveniently by means of a first injector and the second injector which are communicated on the same pipeline, the full-sealed sampling efficiency of the mutual inductor insulating oil is improved, and the sampling difficulty of operators is reduced; by means ofan injector fixation box with a limiting belt and fixation grooves, sampling operation of the operators is more reliable and convenient, and the full-sealed sampling efficiency of the mutual inductorinsulating oil is further improved. Therefore, by means of the full-sealed sampling device for mutual inductor insulating oil and the sampling process using the full-sealed mutual inductor insulatingoil sampling device, the quality of obtained insulating oil samples can be guaranteed, the sampling efficiency of the insulating oil can be notably improved, the sampling operation difficulty of theoperators is reduced, and the device and the process have important popularization and application value.