By covalently modifying 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (ligand) and 4-amino-1,8-naphthalic anhydride (fluorophore) onto the surface of silicon nanowires (SiNWs) and subsequently complexing them with copper ions (Cu²⁺), a SiNWs-based fluorescent sensor for sulfide anions (S²⁻) was realized. Based on such a ligand/Cu²⁺approach, the new type of sensor realizes rapid sensing of S²⁻, and exhibits high sensitivity and selectivity for S²⁻ in water. Moreover, the as-prepared SiNW arrays-based sensor was successfully used in real time and in-situ monitoring of S²⁻ in running water by directly inserting it into the water. The present SiNW arrays-based sensor can be developed into a portable commercial device applied in environmental analysis after further optimizing the technique and finely quantifying the response of the sensor.