Biochemical sensing is essential toward gaining a full understanding of various physiological and pathological events. The in vivo level of hydrogen sulfide (H2S), the third endogenous gaseous transmitter, is closely related to its biological functions at different phases of the cell division cycle. Here we report a facile strategy for H2S sensing in live cells at different phases of cell division by developing a fluorescent nanosensor with double-strand DNA (dsDNA)-stabilized silver nanoflakes (AgNF@dsDNA). The sensing principle is based on selective etching of AgNF@dsDNA by H2S, followed by conversion to Ag2S. AgNFs initially act as quenchers through surface energy transfer, and then its etching leads to fluorescence recovery of modified fluorophore and efficient fluorescence resonance energy transfer (FRET) between two fluorophores. The changes of FRET signal as the readout successfully enable semiquantitative imaging of endogenous H2S alterations in live cells at G1, S, and G2, followed by the cycle of mitosis and cytokinesis. The optimized nanosensor has an excellent linear response in the concentration range of 1-10 μM Na2S. It can also differentiate G0 from G1 and other cell cycle steps through fluorescence imaging of changes in the level of endogenous H2S in cytoplasm during cell division cycle. Thus, the present study paves the way toward utilizing new Ag nanomaterials for biological imaging and sensing in live cells during different phases of the cell division cycle.