The microscopic response measurement of material dynamics was researched experimentally under the loading conditions of gas gun loading. Based on a flash X-ray source with the half width of 25 ns， a real-time X-ray diffraction diagnostic system was developed by using integral record devices. The measuring principle of X-ray diffraction system was introduced. Due to the duration of shocked state in the probed region and the output timing jitter of the X-ray source， the difficulty of system synchronization for X-ray pulse and shock wave in arriving probe region was discussed. Finally， the method to realize the synchronization of the X-ray pulse with the shock wave was achieved by utilizing a fine multilayered target and a piezoelectric pin with ns response time， and a real time X-ray diffraction image of LiF in the peak compressed state was obtained under gas-gun loading. Experimental results indicate that the lattice compression of LiF is 1.73% when shocked pressure is 2.33 GPa. The experimental technique provides an effective means for research of the microscopic response under a gas-gun loading experiment.