investigations indicated that H2S plays a cytoprotective effect under endoplasmicreticulum stress. Currently, it is still a challenge to design effective methods for ratio detection of endoplasmicreticulum H2S. Herein we are the first to construct a ratiometric near-infrared fluorescentprobe (M-H2S) for sensing H2S in the endoplasmicreticulum. M-H2S has high selectivity and sensitivity toward H2S (LOD =