The measurement of tiny displacement is one of the applications of holographic interferometry，and the digital holography，which is a combination of the traditional optical holography and the digital technology，is a relatively new method of getting optical information. In this paper，the technology of digital holography is applied to the existing physical experiment teaching of optical holographic，and the tiny displacement variables of aluminum plate which is derived from the effect of external force，is measured by digital holography comparison method. According to the experimental data measured，Young's modulus of aluminum plate is obtained by the calculation formula，then which is compared with the measurement result of traditional optical holography method under the same experimental environment and the given standard values of aluminum plate. The experimental results show that the digital holography comparison method does not only omit the processing procedure in optical holography such as optical exposure and chemical wet treatment etc.，shortens the experimental operation time，but also reduces the influence of external environment factors，improves the accuracy of the measurement result. The relative error between the measurement result acquired by this method and the given standard value is 3.9%.