Human　serum　albumin　(HSA)　and　hydrazine　(N2H4)　are　known　biomarkers　and　damage　agents　of　liver　function　activity,　respectively.　However,　the　mechanism　of　association　between　HSA　and　N2H4　in　the　liver　remains　unexplored.　Herein,　we　report　a　naphthalimide-based　smart　fluorescent　probe　NI-2　for　the　N2H4　mediated　cascade　detection　of　HSA　(N2H4　∩HSA).　Results　showed　that　the　levulinate　recognition　group　on　NI-2　is　ammonolyzed　within　seconds　in　response　to　N2H4,　releasing　the　compound　NI-OH,　triggering　a　hypsochromic　shift　of　the　emission　to　400　nm;　while　with　the　coexistence　of　HSA,　the　entry　of　NI-OH　into　the　hydrophobic　cavity　of　HSA,　resulting　a　bathochromic　emission　shift　to　670　nm.　We　have　further　revealed　the　reaction　mechanism　of　NI-2　cascade　reacting　with　N2H4　∩HSA　through　HRMS,　replacement　experiment　and　molecular　docking　method.　NI-2　has　been　successfully　applied　in　detecting　N2H4　∩HSA　in　human　urine　quantitatively　and　N2H4　in　water　samples　or　plants.　A　qualitative　test　paper　strip　model　for　quick　response　of　N2H4　and　N2H4　∩HSA　has　also　been　established.　Moreover,　NI-2　can　be　applied　in　bioimaging　of　HepG2　cells　and　zebrafish,　indicating　that　NI-2　can　be　a　potential　tool　for　the　study　of　liver　damage.　©　2023　Elsevier　B.V.