Abstract: Reactive sulfur species (RSS) are important in cellular physiology and pathophysiology．For early diagnosis and therapy it is important to detect RSS rapidly and accurately in biological systems．Fluorescence-based detections are convenient and effective at the molecular level．RSS are generally nucleophilic, therefore nucleophilic substitutions are the common mechanism for RSS fluorescence detection．Typical fluorescent RSS probes for H₂S, glutathione (GSH), cysteine (Cys) are reviewed, with a discussion on different response mechanism．Future directions and opportunities for new fluorescent RSS probes are put into perspectives．