Abstract: Along with the increasing deterioration of the global environment and improvement of environmental protection consciousness，the ship diesel engine exhaust emission has aroused people's attention． Through the research on diesel engine combustion characteristics and EFI engine structure，the structure was optimized to achieve energy conservation and emissions reduction; optimization measures were took to study the influence of the intake on diesel engine combustion characteristics; the feasibility of diesel engine No-Nitrogen( O2 ＆CO2 ) combustion was discussed through experimental study; modern advanced combustion technology characteristic was studied and its application was prospect on Marine diesel engine; finally，the NOx processing technology after the diesel engine was stated． The integrate use of technologies before，inside or after diesel engine， would be the future research direction for energy conservation and emissions reduction．