Abstract: Multi-quantum well laser diodes and their components were irradiated by gamma-ray up to the total ionization dose of 5.5×10⁴ Gy （Si）. The investigated multi-quantum well laser diodes are quite resistive to gamma-ray irradiation because their P-I characteristics, I-V characteristics and central wavelength have little changes. For laser diode component in which optical window, coupled lens and optical fiber and so on are included, its optical performance is degraded by gamma-ray irradiation. The output optical power of laser diode component decreases with total ionization dose; however, the slope efficiency increases gradually with natural annealing at room temperature without biasing after ceasing irradiation.