Combined with the actual situation of the presence of fine cracks on the inner wall of a small number of pipe sections during the acceptance of the duplex stainless steel pipe section of a gas field group development project in the western South China Sea， the endoscopic detection technology was developed and the on-site visual inspection of the inner wall of the duplex stainless steel pipe section was realized. The inspection technology uses a standard optical probe to scan the inner wall of the pipe and archive the inspection results in a video and picture format on a storage device through a standard transport/storage chassis device to create a visual electronic file of the inner wall of the duplex stainless steel pipe section. The field application results show that the endoscope detection technology can effectively and effectively eliminate the defects caused by the inner wall of the pipeline such as cracks， folds and scratches in the production process. The detection technology has achieved good results in engineering and practical， and can be used for similar projects in the future. It can provide experience for reference.