GaAs/AlAs　distributed　Bragg　reflectors　(DBRs)　are　widely　used　in　the　gain　chips　of　1　mu　m　wave　band　semiconductor　disk　lasers　(SDLs)　as　an　end/folded　cavity　mirror.　Because　the　generated　redundant　heat　in　the　active　region　of　a　gain　chip　mainly　dissipates　through　the　DBR,　thermal　conductivities　of　DBRs　are　crucial　for　the　output　performance　of　SDLs.　For　the　purpose　of　more　reasonable　semiconductor　wafer　design,　to　improve　the　thermal　management　of　SDLs,　accurate　thermal　conductivities　of　DBRs　with　various　layer　thicknesses　are　under　considerable　requirement.　By　the　use　of　the　equilibrium　molecular　dynamics　(EMD)　simulation　and　the　Tersoff　potential,　thermal　conductivities　of　GaAs/AlAs　superlattices　with　different　layer　thickness　are　calculated,　and　computed　results　are　compared　with　reported　data　to　verify　the　validity　of　the　EMD　simulation.　The　computed　thermal　conductivities　of　GaAs/AlAs　DBRs　using　the　EMD　method　show　significant　reduction　in　contrast　to　the　bulk　value.　Compared　to　EMD　simulation,　analytic　methods　result　in　smaller　values　of　thermal　conductivities　and　get　close　to　the　bulk　value　much　more　slowly　with　increasing　layer　thickness.　In　the　layer　thickness　of　interest　(60-100　nm),　the　Matthiessen　rule　with　alpha　=　1　for　GaAs　and　alpha　=　0.5　for　AlAs　is　a　practicable　tool　for　thermal　conductivity　estimation.　(C)　2017　Optical　Society　of　America