It is of great importance to detect hydrogen sulfide (H2S) simply and sensitively for its role in various physiological processes as well as its inherent toxicity. In this work, two 3-Hydroxychromone (3HC) derivatives were prepared from 3HC-N3 based on HS− mediated reduction of azides, which was found to recognize G-quadruplexes (G4) with strong fluorescence emission through strong π-π stacking interactions and hydrogen bonding. Moreover, the mixture of 3HC-N3 and G4 was used as the H2S sensor with a limit of detection (LOD) as low as 2.64 nM in aqueous solution, which was much lower than most of current approaches. Given the fine performances and striking properties, this G-quadruplex-selective fluorescent turn-on probe would achieve a promising application of H2S detection in low fluorescence interfering environment samples.