Whispering gallery mode is a type of optical mode where photons move in a quasi-two-dimensional plane, and the total reflection occurs at the boundary of the microcavity without reflecting out of the cavity. This mode has a high Q value and small mode volume, and it is extremely sensitive to changes in the surrounding environment. A broadband fluorescence can be transformed into narrow-spectrum laser output by using the whispering gallery mode. In this paper, polystyrene microspheres doped with the dragon green fluorescent dye are used as whispering gallery mode optical microcavity. Through the phagocytosis of cells, the fluorescent microspheres reach inside cells and then are pumped by nanosecond pulsed laser to achieve the output of whispering gallery mode laser in cells. In comparison with the laser output in the pure-water environment, a redshift of the intracellular fluorescent microsphere whispering gallery mode resonance emission can be observed, and the redshift is related to cell type; therefore, it can be used for unlabeled identification of cell type.