In　order　to　analyze　the　thermal　characteristic　of　GaAs-based　laser　diodes　during　degradation,　aging　tests　were　carried　out　under　the　conditions　of　the　constant　current　stress　for　808　nm　GaAs-based　laser　diodes.　The　temperature　of　active　layer　and　the　thermal　resistance　were　investigated　by　using　electrical　method.　It　was　found　that　the　temperature　of　active　layer　raise　with　the　increase　of　aging　time,　while　thermal　resistance　had　not　changed　during　aging　tests.　At　the　same　time,　the　electrical　and　optical　properties　were　measured,　which　indicated　that　the　main　reason　for　degradation　was　the　increase　of　nonradiative　recombination　in　the　active　layer.　The　results　show　that　the　degradation　of　the　laser　diodes　can　be　observed　effectively　through　thermal　property　measuring　by　using　electrical　method.　The　experimental　results　establish　the　foundation　of　improving　the　thermal　management　technology　and　thermal　properties　of　laser　diodes.