Abstract: The power supply of space nuclear reactor has attracted much attention because it can meet the demand of energy supply with high energy density for space activities such as deep space exploration, orbit propulsion and planetary base. In view of the degradation of electronic components caused by reactor neutron radiation damage, the impact of reactor neutron radiation damage in electronic components should be considered in spacecraft with space nuclear reactor power supply. The long-term operation of space solar cells in orbit will be affected by reactor neutron radiation damage. Both nuclear radiation and space radiation damage will induce displacement damage of space solar cells, resulting in degradation of device performance and even failure of function. GaInP/GaAs/Ge triple junction solar cell is the core component of space power supply system of spacecraft at present. Its radiation damage will lead to performance parameter decline and even cause the function failure of solar power supply system of spacecraft. In order to obtain the experimental results of reactor neutron radiation damage in GaInP/GaAs/Ge triple junction solar cell, the open circuit voltage (V_oc), short circuit current (I_sc) and maximum output power (P_m) of GaInP/GaAs/Ge triple junction solar cell were analyzed by the experiment of radiation damage effect under the different fluences of 1 MeV equivalent neutron. The results show that the degradations of V_oc, I_sc and P_m increase with the increase of neutron radiation fluence when the neutron radiation fluence range is 1×10¹¹-1×10¹⁴ cm⁻². The degradation of P_m is 38.66% when the neutron radiation fluence is 1×10¹⁴ cm⁻². The degradation of P_m is serious than that of V_oc and I_sc. The degradations of V_oc, I_sc and P_m irradiated with different neutron fluence were fitted, and the characteristic curves of different electrical parameters with different neutron radiation fluence were obtained. The attenuation amplitude of the performance of GaInP/GaAs/Ge triple junction solar cell with different neutron fluences could be predicted. In addition, the simulation of neutron radiation damage effects on GaInP/GaAs/Ge triple junction solar cell was carried out. The damage mechanism of GaInP/GaAs/Ge triple junction solar cell performance degradation induced by the reactor neutron radiation damage was analyzed. Finally, the experimental results of normalized P_m degradation at different displacement damage doses induced by neutron and proton radiation were compared.