[en] An experimental neutral beam injection system, called as the NB Test-stand(NBTS), was developed and being operated until this time from 1996 in the Korea Atomic Energy Research Institute(KAERI). The KAERI has supported the design and fabrication of power supply(PS) system, control and data acquisition(CODAQ) system, and beamline(BL) system for the first KSTAR NBI(NBI-1), based on the experience of development and experiments in the NBTS. Therefore, the KAERI was involved in the effective development of PS system, CODAQ system, and BL system for the NBI-1 device. The KAERI has participated in the beam extraction and initial operation of NBI-1 system, based on these experiences of design, fabrication, and operation for the NBI device, and has developed the optimal and reliable operation technologies for the KSTAR NBI-1 device. The KAERI has done the effective arc discharge experiments in the NBI-1 system and has developed the optimal ion beam and neutral beam extractions and neutral beam injection technology. Therefore, the KAERI has importantly and critically contributed the injection of deuterium neutral beam into the KSTAR core plasmas. The operation and maintenance technologies of NBI system, developed in the NBI-1 device, is convinced of the important basis for the development of NBI-2 system in the future