This paper describes how we design engine mount layout, in order to isolate a machine from engine vibration. Natural frequency of vibration isolation system is calculated by Finite Element Method. We focus on the exciting force direction and mode vectors calculated by FEM, and optimize engine mount layout. In the optimization process, we use Modal Assurance Criterion (MAC) to track mode shape which is corresponded with exciting force, and create the maps of MAC value and natural frequency against design parameters. Proper engine mount layout is searched within our design parameters. Finally, multi body dynamics model of engine is constructed and the effect of mount layout which is optimized is confirmed. As a result, the transfer force is reduced 75 % against original design at maximum point.