For long-pulse negative ion–based neutral beam injection (NNBI) experiments, an automatic recording system was designed. The data processing algorithm of neutral beam injection was implemented on the basis of existing methods, and different experimental data were processed in a mode-based method according to the physical characteristics of the neutral beam injection experiment. Based on MDSplus segment storage technology, the range of recorded data was determined by intercepting the segment sequence number of the time series data. LabVIEW was used to achieve the efficient and accurate transmission of experimental processing data. A set of tests demonstrates that the NNBI auto-recording system meets the requirements of the NNBI experience in data processing accuracy (normalized mean square error [NMSE] < 0.04), data transmission accuracy (>98%), and data affect presentation. This system not only obviously improves the work efficiency, but also provides more reliable data sources for the intelligent analysis and processing of the NNBI system.