The invention discloses a multi-junction solar cell and AC electroluminescence measuring method and device of each sub cell, relating to a solar cell AC electroluminescence test. The testing device is provided with an AC drive circuit, an optical module, a vidicon, a spectrograph and a computer. The output end of the AC drive circuit is connected with a solar cell array; the optical module is provided with a filter plate, a battery of lens and a speculum; the filter plate, the battery of lens, the speculum and the vidicon are on the same optical axis; reflecting beams of the speculum are transmitted to the receiving port of the spectrograph; and the output end of the vidicon is connected with the computer. A multi-junction solar cell sample is put on a sample table; the spectrograph is utilized to measure the electroluminescence light spectrum of the multi-junction solar cell to obtain the light-emitting band of each subjunction; a tested light spectrum is selected by the filter plate; the testing range of the cell sample is selected to obtain an AC electroluminescence image; and the computer processes data to obtain the information of the process injury and crystalline material defect of the solar cell and each sub cell component thereof.