In this paper, the deformation fields of LY12 crack samples loaded by an SHTB are real-time investigated with the time interval of 10 µs by an optical system, which consists of a high-speed camera, a flash light, a frame grabber and a synchronization device with the delay-time less than microsecond. The cracks are preset by using the three-points bending method in a MTS fatigue machine. The crack is 2mm long with a flare angle of 60 degree. During the experiments, the dynamic deformation images are captured by the high speed camera and analyzed by newly developed software based on Digital Correlation theory. And the displacements fields near crack-tips according to the changes of the flare angle and radius during the impact process are obtained. Experimental results acquired in this paper are proofed, by compared with the theoretical calculations.