<p>Hull impact response is a focus of attention in issues such as impact environment, vibration and noise, and structural damage. To a certain extent, the hull structure can be simplified into a beam model. Under impact loads, the beam model usually exhibits dynamic responses that are a superposition of overall low frequencies and local medium-high frequencies. Currently, scholars usually conduct research independently on the responses of each frequency band, while the mechanism of how structural response evolves from the high frequency to the low frequency is still unknown. In this paper, the entropy-theoretic characterization method is proposed. The effects of load amplitude, load type, statistic element size and element type on the entropy increase process and relaxation time are further investigated by the full free beam model. Results show that the evolution process of impact response of beam structures includes three stages, and the definition of structural response entropy can effectively reflect the evolution process of structural response, which can be used as a quantitative index to effectively describe the characteristics of structural response evolution and will provide new basic theory support for engineering applications.</p>