As　one　of　the　health　indicators,　intracellular　pH　plays　important　roles　in　many　processes　of　cell　functions.　Abnormal　pH　changes　would　result　in　the　occurrence　of　inflammation,　cancer,　and　other　diseases.　Thus,　it　is　of　significant　importance　to　develop　effective　techniques　for　sensitive　detection　of　pH　changes　for　the　clinical　diagnosis　of　various　diseases　related　to　cells.　In　this　paper,　1,2,4-triaminobenzene　hydrochloride　was　explored　as　an　organic　molecular　fluorescent　probe　for　sensitive　and　selective　detection　of　intracellular　pH　changes　for　the　first　time.　Due　to　the　protonation　and　deprotonation　of　amino　groups　of　the　probe,　its　fluorescent　intensity　at　599　nm　or　the　ratio　of　absorbance　at　505　and　442　nm　has　a　good　linear　relationship　with　pH　values　in　the　range　of　5.0-7.0.　Benefiting　from　the　excellent　physical　and　chemical　properties　of　1,2,4-triaminobenzene　hydrochloride,　the　fluorescent　probe　has　good　water　solubility,　low　toxicity,　high　photostability,　great　reversibility,　good　cell　penetration,　fast　response　speed,　and　so　on.　As　a　proof-of-concept　demonstration,　the　proposed　probe　is　employed　for　the　fluorescence　imaging　of　cells　and　mouse　tissue　sections　with　satisfactory　performance　in　pH　differentiation.　Additionally,　the　probe　was　successfully　employed　to　prepare　test　strips　as　a　kind　of　point-of-care　testing　device　to　detect　ammonia,　which　showed　great　potential　in　practical　applications.　©　2021　American　Chemical　Society.　All　rights　reserved.