The invention discloses a diesel generating set with a sound reduction device in the technical field of diesel generating sets. The diesel generating set is arranged on the top of a base. A rotating shaft is arranged on the left side of the top of the base. The whole diesel generating set is covered. A sound reduction cover plate is composed of a sound reduction interlayer and a steel wire sound reduction layer and has a good sound isolation effect. It can be avoided that noise generated when the diesel generating set works comes out; and meanwhile, workers can conveniently conduct daily repair and maintenance, and the diesel engine set can be repaired and maintained by rotating the sound reduction cover plate through the rotating shaft. Two sound reduction layers are arranged in an innercavity of the base and include the upper sound reduction layer and the lower sound reduction layer. Primary sound reduction and sound isolation are conducted on the noise generated when the diesel generating set works through the upper sound reduction layer. When the sound is transmitted to the lower sound reduction layer, comprehensive sound reduction and sound isolation can be conducted on the sound through a plaster board sound absorption plate layer and a sound absorption net groove panel layer, and sound reduction and sound isolation can also be conducted through partition layers with different through hole numbers at the same time.