High-temperature　phosphorescence　(HTP)　materials　have　attracted　considerable　attention　owing　to　their　expanded　application　prospects,　whereas　they　still　suffer　from　severe　deactivation　in　polar　media,　limiting　their　reliability　and　utility.　Here,　we　present　an　efficient　multivalent　assembly　strategy　to　achieve　high-temperature　liquid-phase　phosphorescence　(HTLP).　The　supramolecular　assembly　of　multivalent　modules　leads　to　extremely　robust　hydrogen-bonding　networks,　which　firmly　immobilize　the　organic　phosphors　and　protect　triplet　excitons　from　annihilation　in　high-temperature　polar　media,　resulting　in　excellent　HTLP　emission.　Moreover,　the　photophysical　properties　of　HTLP　are　significantly　enhanced　by　boosting　multivalent　interactions　using　multitopic　phosphors,　demonstrating　a　visible　afterglow　of　5　s　in　boiling　water,　more　than　2　s　in　dimethylsulfoxide　at　460　K　(187　degrees　C),　and　a　long　lifetime　of　70.3　ms　in　N-methylpyrrolidone　at　476　K　(203　degrees　C).　Based　on　their　fluidity　and　robust　HTLP　emission,　in　situ　microcracks　detection　of　high-temperature　operating　instruments　and　spatial-time-temperature-resolved　anticounterfeiting　are　demonstrated.