The invention discloses a measuring method of up-conversion intermediate energy level lifetime of erbium ions and relates to the measuring method of fluorescence lifetime, and the measuring method can solve the problems that the existing measuring method of the infrared fluorescence lifetime needs an expensive infrared detector, the testing process is complicated, double beams and the delay change between the double beams need to be introduced, and the testing difficulty is great. The method adopts a delay signal generator, a short pulse laser, a high voltage pulse generator, an enhanced charge-coupled device and a grating spectrometer for constituting a testing system, and fluorescence emitted by a tested material by pulse radiation enters into the spectrometer for testing the light intensity; and the corresponding visible light intensities under different excitation frequencies are measured under the condition of keeping the single pulse energy unchanged, an I-1/f relation map is drawn out, then fitting is carried out by utilizing the formula, and the fitted tau is the up-conversion intermediate energy level lifetime. The single beam is adopted and the visible light detector is used for measuring the infrared energy level fluorescence lifetime, the measuring process is simple, and the measuring method can be used for measuring the fluorescence lifetime of Er3+ doped materials.