Objective To explore the application of near infrared fluorescent dye C-dots in cell labeling.Methods B16 melanoma cells were cultured with C-dots of various diameters.The distribution of C-dots in cells was observed by laser confocal fluorescent microscope.The proliferation of both C-dots-labeled and unlabeled cells were measured by MTT colorimetry.The viability of labeled cells was checked by trypan blue staining.Results C-dots with diameter of 5 or 10 nanometers can be used to label cells.The near infrared fluorescence of C-dots was taken into the cells and observed on the cellular membrane.No difference of cellular viability was found between the labeled and unlabeled cells.Conclusion C-dots can be used as an intracellular marker for the research on trace and proliferation of cells.