Mercury　(Hg)　is　an　exceedingly　toxic　heavy　metal　which　leads　to　grievous　nonbiodegradable　contamination　and　human　health　threat.　Thus,　developing　a　practical,　quick,　effective　and　labor-saving　method　for　detecting　Hg2+　is　of　great　significance.　In　this　study,　we　rationally　design　two　novel　near-infrared　(NIR)　monothiosquaraine-based　probes　MTSQ-1　and　MTSQ-2　for　tracking　and　bioimaging　of　Hg2+　with　the　mercury-desulfurization　strategy.　MTSQ-1　and　MTSQ-2　show　ultrahigh　sensitivity,　superb　selectivity　and　rapid　response　for　spotting　of　Hg2+　in　vitro.　We　find　that　it　is　the　intramolecular　hydrogen　bond　between　the　carbonyl　oxygen　of　the　squaraine　core　and　the　ortho-hydroxyl　substituent　of　the　anilinyl　moiety　that　promotes　the　desulfurization　of　the　probes,　inducing　enhanced　fluorescence　emission.　Related　sensing　mechanism　has　been　fully　discussed　through　experimental　methods　and　theoretical　calculations.　Meanwhile,　MTSQ-1　has　been　used　in　detection　of　Hg2+　in　river　samples,　and　MTSQ-2　encapsulated　in　β-CD　possesses　good　ability　for　imaging　of　Hg2+　in　HeLa　cells　with　high　signal-to-background　ratio.　©　2022　Elsevier　B.V.