In this paper, a concept of sensitivity analysis focusing on vibration energy is proposed. Although research on the vibrational energy flow has been conducted, the design method to control it has not been established. In this study, an equation of sensitivity to predict the change of vibration energy due to mass addition, damping and stiffness additions are also derived, and their validities are examined using the spring mass system, and appropriate structural changes are discussed. The reduction of vibration energy was carried out by the equation of sensitivity. Next, the proposed equations of sensitivity are generalized and expanded to general structures modeled by the finite element expressed using Frequency Response Function (FRF). The model was divided into separate systems at the evaluation points, and the vibration energy was calculated from the velocity and transmission force from each FRF. The change in vibration energy due to structural changes was determined using the change in FRF. The vibration energy at the specific point was reduced by modifying the structure based on the proposed equation of sensitivity. This paper confirms the validity of the proposed equations of sensitivity for mass addition, damping and stiffness.