Abstract: A well in South China Sea had a neutron source falling accident during the drilling process. A series of treatment measures and schemes were formulated by selecting and using special fishing tools, combining with the judgment of downhole conditions and the structural analysis of logging tools, and the radioactive source was successfully salvaged out of the well. Based on the analysis of the process of salvaging radioactive sources, this paper puts forward the key steps and measures of salvaging radioactive sources in large displacement wells, and provides reference for similar complex situations in the future.