High-power　vertical　cavity　surface　emitting　lasers　(VCSELs)　are　widely　used　in　optical　communication,　optical　storage,　optical　interconnection,　sensing,　and　other　fields.　High-power　VCSELs　usually　adopt　a　high-density　array　layout,　and　temperature　is　one　of　the　key　factors　affecting　their　performance.　In　this　work,　the　thermal　characteristics　of　the　VCSEL　array　with　1273　elements　have　been　studied.　A　series　of　photoelectric　characteristics　such　as　the　working　voltage,　output　optical　power,　slope　efficiency,　electro-optical　conversion　efficiency,　and　spectrum　of　the　device　have　been　analyzed　through　a　precision　temperature　control　system.　According　to　the　relationship　between　the　measured　wavelength　shift　and　the　dissipated　power,　it　is　calculated　that　the　thermal　resistance　value　of　the　device　increases　from　1.319　℃/W　to　1.952　℃/W,　and　the　temperature　rise　of　the　active　area　is　extracted.　It　can　be　seen　that　more　temperature　rises　in　the　active　region　at　higher　ambient　temperature　for　a　given　injection　current,　with　a　maximum　value　of　105.6℃.　A　thermoelectric　coupling　model　was　established　to　simulate　the　thermal　distribution.　The　equivalent　array　method　is　employed　to　simplify　the　high-density　array.　The　simulated　results　agree　well　with　the　measurement.　As　the　ambient　temperature　rises,　the　thermal　crosstalk　phenomenon　in　the　VCSEL　array　becomes　more　obvious.　Heat　diffusion　becomes　more　difficult,　resulting　in　more　heat　accumulation　inside　the　device.　The　internal　loss　of　the　device　is　severe　and　the　gain-cavity　mode　is　seriously　mismatched,　so　the　photoelectric　performance　decays　sharply.　This　research　provides　important　guidance　for　the　optimization　and　application　of　future　devices.　©　2023　SPIE.