The multi-body dynamics model of the X6170ZC diesel is established to analyze vibration and acoustic noise. The high quality finite element and simulation models are developed, and nonlin-ear springs are used to imitate the joints of engine components. The acoustic behavior of the struc-ture is evaluated by the velocity of surface vibration. The noise level is reduced by improving the structure of the engine. The result shows that the surface vibration velocity level is decreased about 3.7 dB (A) at-1 600 Hz after the optimization. Based on the contrast between the two structures, it is concluded that through structure design the combined noise can be reduced, and the virtual de-sign mode of diesel engines is feasible.