The invention discloses a combined desulphurization and denitration device and method of a marine
diesel engine. The
exhaust gas of the
diesel engine is divided into two paths, wherein one path enters a denitration channel A and is recirculated to an air cylinder to participate in burning so as to lower the
NOx emission of an engine; the other path enters a desulphurization channel B and is discharged to ambient
atmosphere after being subjected to desulphurization
processing. In the denitration channel A, the
exhaust gas flows through components including a one-way stop valve, a
Venturi scrubber, a cooler, a cleaning device, a blower and the like, particles and SO2 in the
exhaust gas are removed through
processing processes including pre-washing, cooling, washing, pressurizing and the like, and finally, the exhaust gas is mixed with
fresh air from the intake channel of the
diesel engine to enter the air cylinder and participate in burning; in the desulphurization channel B, the exhaust gas is discharged into the environment
atmosphere after being subjected to particle removal by washing
tower desulphurization. The Tier III requirement of IMO (International Maritime Organization) on
marine fuel sulphur content and
NOx emission in the exhaust gas can be met, and meanwhile, the
corrosion and the abrasion on an engine compressor, a cylinder liner and the like by the exhaust gas can be lowered.