Current　seismic　design　codes　worldwide　mainly　address　mainshock　defense,　largely　overlooking　aftershock　impacts　on　structural　damage.　Most　studies　on　the　seismic　performance　of　bridge-track　systems　(BTS)　consider　only　the　effect　of　a　single　mainshock.　To　explore　the　damage　mechanism　of　the　BTS　under　aftershocks,　a　threedimensional　finite　element　model　of　the　BTS　was　established　in　OpenSEES.　Taking　site　effects　into　account,　a　mainshock-aftershock　sequence　was　synthesized　using　response　spectrum　method　combined　with　a　stochastic　approach.　A　lateral　input　method　was　used　to　conduct　nonlinear　dynamic　response　analysis　of　the　BTS　under　mainshock-aftershock　sequences.　The　post-earthquake　residual　deformation　of　mainshock-aftershock　sequences　with　different　polarities　was　analyzed　across　four　site　conditions　based　on　mainshock　damage　characteristics.　The　seismic　response　differences　of　aftershocks　on　structures　across　four　types　of　sites　were　compared.　Furthermore,　different　peak　ratios　were　analyzed　to　reveal　the　BTS　failure　mechanism　under　mainshockaftershock　sequences.　The　results　show　that　class　IV　sites　exhibit　the　highest　seismic　response　under　mainshock　conditions,　with　damage　primarily　located　in　bearings　and　sliding　layer.　When　considering　site　effects,　aftershocks　of　the　same　polarity　as　the　mainshock　cause　more　severe　damage　to　the　BTS,　and　class　II　sites　are　more　sensitive　to　aftershocks,　with　residual　deformation　increasing　by　up　to　196.1　%　after　the　earthquake.　When　peak　ratio　exceeds　4,　the　damage　extent　from　aftershocks　to　some　components　can　be　neglected.　The　peak　displacement　of　the　mainshock　significantly　affects　the　damage　from　aftershocks.　Conclusions　drawn　can　be　applied　in　the　actual　seismic　design　and　also　can　provide　the　in-depth　insight　into　the　damage　analysis　and　failure　mechanism　of　high-speed　railway　bridge-track　systems.