In the air and the vacuum, triple-junction gallium arsenide (GaAs) solar cells are irradiated by the 1070 nm continuous-wave (CW) laser and the current-voltage curves of cells before and after laser irradiation are tested. By using the laser beam induced current (LBIC) measuring system and the X-ray photoelectron spectrometer (XPS), the damage situations of triple-junction GaAs solar cells are analyzed. The results show that, when the laser power density is 8.4 W/cm2 and the irradiation time is 10 s, the bottom-cell Ge is fused and short-circuited in the air, and the top-cell Ga0.5In0.5P and the bottom-cell Ge are both short-circuited in the vacuum, which means the bottom-cell of triple-junction GaAs solar cells is the most easily damaged part and the cell is easier to be destroyed in the vacuum than in the air. These study results can provide references for the research on laser wireless energy transmission and the laser damage mechanisms of triple-junction GaAs solar cells.