The widespread use of room temperature vulcanized silicone rubber in high-voltage outdoor insulation enhances the overall insulator's resistance to pollution flashovers upon application, thus synergizing the advantages of both inorganic and organic materials. Due to cost considerations, many manufacturers opt to incorporate a higher proportion of calcium carbonate into RTV coatings in practical manufacturing scenarios. Through a comparative analysis of the aging behavior and mechanisms of RTV anti-pollution flashover coatings with varied calcium carbonate content subjected to thermal oxygen aging experiments, the impact of calcium carbonate filler on coating aging in actual environmental conditions was examined. The addition of calcium carbonate facilitates the reaction of functional groups on the coating surface, accelerating the aging of the coating surface. However, it also provides a certain degree of heat resistance in high-temperature environments. The investigation into the aging mechanisms of the coating and the assessment of changes in silicone rubber content during aging offer valuable guidance for improving the longevity of the coating.