We　measured　the　response　of　the　facet　temperature　of　the　semiconductor　laser　to　a　single　pulse　current　witha　magnitude　of　microseconds　by　using　transient　thermoreflection　method,　and　then　calculated　the　thermaltime　constants　of　the　laser.　The　thermoreflection　technique　measures　the　reflectivity　of　facet　which　is　affectedby　temperature　in　real　time　and　thus　only　measures　the　thermal　parameter.　In　addition,　we　select　the　fallingedge　of　the　pulse　current　where　current　and　light　dissipate　immediately　during　the　heat　decline　as　the　startingpoint　for　the　study　of　the　thermal　response.　Therefore,　the　electro-optical-thermal　characteristics　of　the　laserare　decoupled　in　the　measurement　process.　The　transient　thermal　response　is　formulated　as　a　second-orderexponential　function　of　time.　The　two　time　constants,　i.e　&　x1d749;&　xdf49;&　x1d7cf;&　xdfcf;and　&　x1d749;&　xdf49;&　x1d7d0;&　xdfd0;,　represent　thermal　conductivity　performanceof　laser　chip　and　device　package,　respectively.　We　studied　the　transient　thermal　behavior　of　the　laser　underunsteady　state　based　on　the　evolution　trends　of　the　thermal　time　constants　with　amplitude　and　width　of　thepulse　current.　When　the　pulse　is　narrow,　the　heat　of　the　device　is　concentrated　in　the　active　region,　even　if　thecurrent　amplitude　is　relatively　large;　With　the　increase　of　pulse　width,　the　heat　generated　in　the　active　regiondiffuses　outward　to　other　layers　of　the　chip　and　heat　sink.　We　also　observed　the　mechanical　deformation　ofthe　facet　in　the　active　region　which　results　from　heat　accumulation,　and　the　heat　generation　is　related　to　lightintensity.