The invention provides a noise reducer for a generator, and belongs to the technical field of noise reduction equipment. The noise reducer comprises a shell, wherein an air inlet and an air outlet areseparately formed in the two ends of the shell; a built-in partitioning plate which is hermetically connected with the inner wall of the shell is arranged in the shell; an air inlet pipe and an air outlet pipe, which are positioned in the shell, are separately arranged on the two sides of the built-in partitioning plate; the air inlet pipe and the air outlet pipe separately communicate with the air inlet and the air outlet; an air inlet partitioning part and an air outlet partitioning part are separately arranged on the outer walls of the air inlet pipe and the air outlet pipe and are separately and hermetically connected with the inner wall of the shell; at least one connecting pipe is arranged on the built-in partitioning plate in a penetrating manner; one end of each of the connectingpipes is positioned between the air inlet partitioning part and the air outlet partitioning part while the other end of each of the connecting pipes is positioned between the air outlet partitioning part and the built-in partitioning plate; and the two ends of the connecting pipe separately communicate with the air inlet pipe and the air outlet pipe. The noise reducer disclosed by the invention has an effect of reducing or lowering noise.