Abstract: In order to study effect of 1070nm continuous wave (CW) laser irradiation on three-junction GaAs solar cells, rear surface temperature and load voltage of a solar cell under different power densities were measured. Under 8.4W/cm² laser irradiation, the temperature increased obviously and load voltage decreased nearly to zero. The load voltage only recovered to 53% of the initial value after irradiation. With the increasing of power density to 11.7W/cm², the load voltage decreased to zero after 2.3s. Furthermore, the cell was damaged and can't be recovered. The results show that the temperature of a solar cell rises significantly and the load voltage deceases when irradiated by CW laser. When laser power density is small, the rise of cell temperature is small and the drop of load voltage is also small. The load voltage can be restored to the initial state with the stop of laser irradiation. When laser power density is large, the rise of cell temperature is large and load voltage decreases significantly. Even with the stop of laser, the load voltage can not be restored to the initial value and the cell is damaged. The experiment results can provide reference basis for the research of damage mechanism of solar cells under laser irradiation.