The effect of adding silica to rubber compound on its, adhesion to brass-plated steel cord was investigated. Silica reduced the curing rate and enhanced the physical properties of the rubber compound, especially after thermal aging, when 20 phr of silica was added, The pull-out force increased considerably with silica loading both before and after thermal aging. Although improvements in the rubber coverage were not significant in the unaged start: with silica loading, they users considerably enhanced after aging, especially after salt solution aging, The adhesion interphase between silica-containing rubber compound and brass film also appeared to differ from samples without silica loading. With silica loading, overgrowth of the adhesion interphase was suppressed, as was the proliferation of sulfides and oxides of copper and zinc to rubber bulb after humidity and salt solution aging treatments, The suppression of the excess growth of the adhesion interphase and the improvement of the rubber properties under thermal, humidity, and salt solution aging conditions are considered to be the effects of silica loading, resulting in good adhesion durability after aging.