The invention relates to an energy-saving and environmental-friendly device for a marine diesel engine. The energy-saving and environmental-friendly device comprises a rotation rate signal acquisition unit, an electric shock signal generation unit and an electric shock output unit. The rotation rate signal acquisition unit is used for acquiring a rotation rate signal of the marine diesel engine, and supplies the acquired rotation rate signal to the electric shock signal generation unit; the electric shock signal generation unit comprises electric shock signal generation modules of fuel viscosity, fuel atomization, metal components and lubricating oil which are respectively used for generating electric shock signals of the fuel viscosity, the fuel atomization, the metal components and the lubricating oil; the electric shock signals are respectively output to a fuel storage tank, a case of an oil expeller, top of a cylinder and a lubricating oil sump of an engine; and the fuel atomization electric shock signal is an impulse signal with frequency of 400,000 times per minute and pulse voltage amplitude of 0-35V and current set according to different rotation rates of the engine. The energy-saving and environmental-friendly device is arranged on the marine diesel engine, which significantly improves fuel saving ratio as well as greatly reduces hydrocarbon emission.