— The influence of proton irradiation on the structure of Nb 3 Sn superconducting materials has been investigated. The irradiation to different proton doses was performed on a cyclotron at the National Research Centre “Kurchatov Institute” (NRC KI). The Nb 3 Sn samples were placed successively pairwise on the beam axis to obtain different degrees of radiation-induced damage at a specified dose. X-ray diffraction (XRD) analysis of irradiated and unirradiated samples was carried out on a synchrotron radiation source at the NRC KI. The results of studies revealed that the diffraction peaks broaden and become weaker with an increase in the concentration of radiation-induced defects. The phase compositions of the samples and dynamics of changes in the found NbO phase under irradiation have been investigated. The change in the lattice period for the irradiated samples is studied. It is shown that the lattice period increases with an increase in concentration of radiation-induced defects.