A test rig is performed to measure power flow and estimate vibrational energy in this paper. Both force signal and acceleration signal of the same location and direction of one point could be simultaneously captured by inserting an impedance head. Subsequently, the power flowing into the foundation is calculated by the time average method, the fundamental frequency method and the second harmonic frequency method respectively. Experimental investigation shows that the harmonic vibration should be controlled, if the operating frequency of vibration source is the fractional frequency of natural frequency. However, due to the negative value which is inevitable during the measurement process of power flow, this study attempts to interpret the cause of the negative power flow from multi-degree of freedoms vibration. Due to the difficulty of measurement, the vibrational energy of the foundation is estimated via the driving impedance and mobility. Finally, the relationship between power flow and vibrational energy is examined by the loss factor.