Dynamic speckle photography of the gear tooth has been achieved by combining a pulsed ruby laser with the external synchronizing trigger signal. Double speckle photograms of the whole mesh period of gear tooth are obtained by accurate time delay. Gear tooth dynamic deformation of the whole mesh period is achieved using the automatic image processing. Testing results show that the trends of gear tooth deforamtion coincide with the calculated ones by the finite element method. The success of the testing provides a new way for the measurement of the rotating gear tooth dynamic deformation.