In this paper，the method of measuring the in-plane displacement field under an impact loading is proposed and is named dynamic digital speckle pattern interferometry. By means of transient digital image capturing system，the undedeformed and deformed images are both stored directly in frame memory to achieve digital interfering. In the end of the paper，the in-plane displacement solution of a semi-infinite plane model is obtained experimentally，which shows good agreement with that by finite element method.