Abstract: A fluorescent probe compound, a preparation method thereof, and a method of imaging and quantifying lysosomal adenosine triphosphate (ATP) at a cell or tissue level through one-photon or two-photon fluorescence microscopy using the compound is disclosed. A fluorescence detection system capable of detecting lysosomal ATP is further disclosed. Since the fluorescent probe compound is found to be capable of selectively sensing and quantifying lysosomal ATP in a cell or tissue, it is expected that the disclosed compound or composition can be usefully employed in the study of various biological reactions or diseases associated with ATP in a living body.