Abstract: Roundness damage is an important index to study the change of mechanical properties of coarse-grained soil. In order to explore the evolution process of roundness damage of coarse-grained soil during shearing, the nature of damage is analyzed qualitatively and quantitatively from the energy point of view. According to the principle of energy dissipation, the dissipation and transmission of energy in the shearing system and individual particle shearing process are analyzed. Based on the elastoplastic mechanics and thermodynamic laws, the roundness damage factor Dr of coarse-grained soil is defined, and the roundness damage model based on energy dissipation is established. The shear strength test is used to study the strength characteristics of granite and pebble particles with different roundness. The granite particles with good observation effect are studied. The evolution process of roundness damage under different normal stresses is studied. The model and test data are analyzed by using MATLAB. The results show that the particles with different roundness (granite and pebbles) decrease with the roundness, and the plastic potential energy transmitted to the interior of the particles increases. It is easier to generate micro-cracks at the corners of the particles to wear the particles and increase the roundness of the coarse particles. The strength characteristics are reduced. There are two damage inflection points in the shear evolution process of coarse-grained soil roundness. It can be divided into three stages: roundness damage response, roundness damage evolution and roundness damage stability. The same type of particle normal stress increases, the energy required to achieve roundness damage in the critical state of damage increases, and the roundness damage factor decreases. Based on the roundness damage model established under energy dissipation, the roundness damage during the shearing process is described. The test results can reasonably reflect the mechanical response of the particle during the roundness damage evolution process.