A method for identifying red tide phytoplankton quickly includes collecting phytoplankton from Chinese east sea where red tide is frequently occurred and culturing them, measuring 3D fluorescent spectrum under condition of exciting wavelength at 200 - 600 nm and emitting wavelength at 200 - 800 nm, setting up original spectrobank after density is normalized, utilizing singular value decomposition method to eliminate interference factor for setting up characteristics spectrobank of fluorescent spectrum, using finally prepared spectrobank as a base to determine out kind and quantity of phytoplankton contained in measured sample.