Thermal　properties　of　multiple　layers　including　distributed　Bragg　reflector　(DBR)　and　multiple　quantum　wells　(MQWs)　used　in　the　semiconductor　gain　element　are　crucial　for　the　performance　of　a　semiconductor　disk　laser　(SDL).　For　the　purpose　of　more　reasonable　semiconductor　wafer　design,　so　to　improve　the　thermal　management　of　SDLs,　accurate　thermal　conductivity　value　of　a　DBR　is　under　considerable　requirement.　By　the　use　of　equilibrium　molecular　dynamics　(EMD)　method,　thermal　conductivities　of　AlAs/GaAs　DBRs,　which　were　widely　employed　in　1　mu　m　wavelength　SDLs,　were　calculated,　and　simulated　results　were　compared　with　reported　data.　Influences　of　the　Al　composition,　and　the　layer　thickness　on　the　thermal　conductivities　were　focused　and　analyzed.