Based on the dynamic light scattering and approximate model, laser speckle contrast imaging (LSCI) is a powerful tool for full-field imaging of blood flow by analyzing the characteristics of speckle space or time intensity fluctuation. Because of the advantages of large imaging area, fast speed and high resolution, the technology is used in biomedical imaging research and clinical diagnosis widely. A lot of research on the theoretical models, imaging methods and applications of LSCI are done by many researchers. This review presents the main improvement on method and applications of LSCI. Moreover, we discuss the concepts about increasing resolution, contrast, imaging penetration, and quantitative ability of LSCI. Finally, we review the applications of LSCI in ophthalmology, microcirculation, neuroscience, dermatology and surgical monitoring.