Taking the large 20 000 TEU LNG/diesel dual-fuel powered container ship as the research object, and combined with the requirements of IGF Code, the composition and functions of nitrogen system required to ensure the safe operation of dual-fuel engine are expounded. Combined with the demands of certain actual ship, the design and configuration scheme of its nitrogen system including the working principle of nitrogen system, model selection of nitrogen generator, and capacity calculation of main equipment are analyzed, and the configuration and model selection scheme of nitrogen system are determined.