The invention discloses a push and pull crossed type noise-reducing and silencing body structure for a vehicle-mounted muting unit and mainly relates to the technical field of noise reduction. The push and pull crossed type noise-reducing and silencing body structure for the vehicle-mounted muting unit comprises an external silencing body, an internal silencing body, a guide rail, a fixing framework, a muting unit and a vehicle-mounted platform; the external silencing body is fixed to the fixing framework; the internal silencing body is fixed at an air exhaust opening of the muting unit; the muting unit is fixed on the vehicle-mounted platform; the internal silencing body and the external silencing body are connected with each other through the guide rail; and therefore, two working conditions of a silencing body extending condition and silencing body retracting condition can be selected according to a working state of the muting unit; the push and pull crossed type noise-reducing andsilencing body structure is mainly mounted at the air exhaust opening of the muting unit so that the noise at the air exhaust opening of the muting unit in the working state is greatly reduced; influences of the noise at the air exhaust opening on noises of other testing surfaces are reduced so that the average value of the noises of the testing surfaces is reduced, and the muting grade of the muting unit is increased; and a broader application range is realized.