For　the　steady-state　identification　of　the　key　variables　in　the　steady-state　optimization,　a　determination　method　was　proposed　for　the　steady-state　identification　of　sample　data　based　on　the　hypothesis　testing.　The　method　could　realize　the　data　steady-state　identification　of　the　isolated　heat-pipe　heat　exchange　system.　Then,　experiments　were　carried　out　by　the　practical　data　with　normal　distribution　characteristics.　The　data　steady-state　was　determined　by　judging　the　change　of　sample　variance.　Finally,　it　was　found　that　the　optimization　cycle　must　be　greater　than　4　minutes.