A pulse X-ray diffraction measurement system is established by using a miniaturized flash X-ray source on gas gun loading experimental platform. The system is used to study the microstructure change of LiF crystal lattice under plate shock loading experiments. Single pulse X-ray diffraction images from LiF crystals are obtained under different shock loading pressures. Experimental results show that crystal lattice of LiF is compressed when LiF crystal is loaded along ［100］ orientation, and the amount of compression is related to the shift of diffraction peak position. Quantitative measurement of material microstructure change under shock compression can be achieved by pulse X-ray diffraction measurement system using miniaturized flash X-ray source. The system described here has advantages such as small size and easy to use, and it provides effective method to study the microscopic mechanism of elastic-plastic deformation.