Damage characteristics of triple-junction GaAs solar cells irradiated by nanosecond pulsed lasers and their effects on photoelectric conversion were studied. The experimental system was established including damage morphology, voltage-current characteristics, and electroluminescence. The gradual decline characteristics of the photovoltaic performance of the cell was analyzed from the material ablation morphology, electrical performance output, and internal damage. On the basis of analyzing the influences of laser energy density, the influence of laser irradiation regions, such as the grid line part and non-grid line part of the cell, was further analyzed. Nanosecond pulsed lasers can cause obvious damage to the cell due to its high peak power. The damage effect of the grid line part of the laser was stronger than that of the non-grid line part, mainly because the function of the grid line electrode was used to collect photo-generated carrier. When the laser radiation fused the cell grid lines, which was used to collect photogenerated carriers, the output power of the cell was reduced. The research conclusions are of great significance for improving the protection capability of the solar cells.