Grain crushing is commonly encountered in deep foundation engineering, high rockfill dam engineering, railway engineering, mining engineering, coastal engineering, petroleum engineering, and other geoscience application. Grain crushing is affected by fundamental soil characteristics, such as their mineral strength, grain size and distribution, grain shape, density and specimen size, and also by extal factors including stress magnitude and path, loading rate and duration, degree of saturation, temperature and geochemical environment. Crushable material becomes a series of different materials with the change in its grading during grain crushing, resulting in a decrease in strength and dilatancy and an increase in compressibility. Effects of grain crushing on strength, dilatancy, deformation and failure mechanisms have been extensively investigated through laboratory testing, discrete element method (DEM) modelling, Weibull statistics, and constitutive modelling within the framework of the extended crushing-dependent critical state theory or the energy-based theory. Eleven papers summarized in this review article for this special issue addressed the above issues in grain crushing through the advanced testing and modelling.