Provided is a nitrogen generating system for ships. The nitrogen generating system consists of the following apparatuses sequentially connected by means of pipelines: a compressor (10), comprising at least one compressing unit (101) used for providing compressed air; a filtering means (70), comprising at least one filtering unit used for filtering the compressed air; a nitrogen generator (20), comprising at least two nitrogen generating units (201) used for generating nitrogen; an optional nitrogen buffer (40); and a flow and pressure regulating means (30) used for regulating flow and pressure. The system does not have a refrigeration dryer and an air buffer tank, and therefore, the system is simple in structure and the investment and energy consumption of apparatuses are reduced; meanwhile, the system can output nitrogen having low flow and high pressure.