Abstract: Based on the refined method for constructing DEM model based on the computed tomography scanning of irregularly shaped (IRS) particles, a random technique for constructing DEM model for IRS rock block is proposed, and 3D DEM models for soil-rock mixture (SRM) which conforms to the macroscopic statistical rule are established. In order to study the mechanical properties and deformation mechanism of SRM with various rock block proportions (RBP), DEM numerical simulations of large scale triaxial tests are conducted. It is noteworthy that with the increase of RBP, the peak strength, residual strength, elastic modulus and axial strain at peak strength all increase. The increase of RBP leads to the increase of shear dilatancy deformation and the decrease of shear contraction deformation. During the initial period of axial loading, the microcracks originate mainly from the contacts between rock particles and soil particles very quickly and then develop in the soil matrix. With the increase of RBP, the proportion of microcracks around the rock particles increases, and local shear bands become more and more irregular and scattered. The rock particles of SRM with high RBP exhibit obvious inter-friction just in the early period, and then their inter-locking and relative sliding appear alternately.