Phycoerythrin is isolated and purified from red algae, which can emit strong fluorescence, it own good absorbance and high quantum yield, and has a wide excitation and emission range in the visible spectrum. Conventional labeling methods can easily combine it with biotin, avidin, and various monoclonal antibodies to produce fluorescent probes, which are used for antibody fluorescence labeling such as fluorescence microscopy detection, fluorescence immunoassay, dual or multi-color fluorescence analysis, cancer cell surface antigen detection, flow cytometry fluorescence measurement, as well as diagnostic and biotechnology applications such as in vivo imaging. B-PE (B-Phycoerythrin) is a fluorescent protein belonging to the highly soluble fluorescent protein family in cyanobacteria and eukaryotic algae. B-PE is composed of alpha Composed of α, β and γ subunits, it exists in the form of (αβ)6γ. The peak values of the absorption band are 545nm (εM=2.41 X106M-1cm-1) and 563 (εM=2.33 X 106M-1cm-1), respectively. B-PE and its closely related R-PE are the most fluorescent phycobiliproteins. B-PE labeled streptavidin, primary and secondary antibodies have been widely used in fields such as flow cytometry and multi-color immunofluorescence staining.