For crushable sand, compared to non-crushable sand, this paper describes the experimental phenomenon of the opposite turning direction of stress–dilatancy curve after the peak stress ratio. Then, based on the first law of thermodynamics, we derive a new stress–dilatancy model which incorporates the derivatives of breakage energy and rearrangement energy to account for the opposite turning hook of crushable sand. In the framework of this model, the mechanism for opposite turning hook is attributable to the breakage-caused change of particle size distribution, which leads to the decrease of the critical stress ratio M and the decrease of the rearrangement-energy-related term. Our model is verified through our triaxial tests on crushable calcareous sand, non-crushable silica sand, and artificial particles, which well depicts the opposite turning phenomenon. Our model is also verified through other crushable sands from two existing literatures.