Studying the dynamic response and failure mechanism of hazardous substances storage cabinet structures under internal combustible gas explosion loads can minimize the consequences of explosion accidents, reducing casualties and property losses, which holds significant engineering and social value. This study used methane mixed with air as the combustible gas in internal explosion tests conducted within a hazardous substances storage cabinet structure. Tests were performed under four gas cloud conditions: 1 m³, 8 m³, 27 m³ and 78 m³. Typical overpressure and displacement time-history curves from internal explosion were obtained, and the dynamic response was analyzed. The results show that the displacement response of the storage cabinet structure synchronized with the load response. As the overpressure load increased, the displacement of the storage cabinet wall increased accordingly, reaching their peak nearly simultaneously. The results of overpressure and structural response tests indicate that the peak value of the overpressure load measured in the test did not follow the expected trend, as the more extensive gas volume did not consistently result in higher peak overpressure values.