To improve the sealing structure performance of the existing converter transformer casing hole, a new sealing and explosion-proof structure was designed. The anti-explosion performance of the structure was analyzed through full-scale blasting tests. The experiment simulated three types of overpressure impact effects, namely general, large, and ultimate, based on three different amounts of explosives, and the appearance, overpressure time history, displacement time history, and residual deformation records was observed. The results indicate that the new sealing and anti explosion structure maintains integrity in both the overall structure and the sealing cover plate under general and large overpressure loads, and the actual displacement of the structure is lower than the design requirements, indicating that the anti explosion ability of the new structure is sufficient to withstand general and large overpressure blasting effects. Under extreme overpressure blasting loads, although the displacement and deformation of the structure have significantly increased, the overall structure remains intact, with only partial cover plate warping caused by anchor bolt detachment. This indicates that even under extreme overpressure loads with large blasting quantities, this new structure still has considerable blast resistance. Based on this experiment, it can be found that the new sealing structure has excellent anti explosion performance, and its anti explosion ability can be further strengthened by strengthening the connection in the future.