In recent years, lighter and more compact car engines have been required to meet the requirements for performance, fuel consumption and collision safety. At the same time, demands for greater vehicle comfort have been increasing every year, making it necessary to reduce engine noise and vibration further. Against this backdrop, the vibration reduction technologies of the engine researched since before. But, the actual design is depend on an experience and trial and error. Because of this, there was no guarantee that the most suitable design within a given period of time. This paper describes the optimization calculation was applied to the development of the new engine.