Neutron diffraction provides a unique scientific guarantee for accurate measurement,analysis and characterization of material properties such as structure,micro-defects and residual stresses of engineering materials,which is an ideal tool for in-depth study of material characterization and life assessment mechanism. This paper outlines the basic principle of neutron diffraction measurement,reviews the application of neutron diffraction technology in the fields of welding stress engineering and life extension technology of nuclear power structure,auxiliary optimization of welding heat treatment process,etc.. Finally,according to the characteristics of neutron diffraction engineering spectrometer,the future prospects of this technology in the field of material research are prospected.