Abstract: Based on the laboratory uniaxial compression test, a numerical model was established by particle flow software and the microscopic parameters were calibrated. The stress-strain curves, the number of micro-cracks, the failure process and the change of microscopic displacement field of gangue cemented backfill samples were studied under different loading rates. The results show that the peak strength and elastic modulus of the sample increase with the increase of loading rate. The number of microcracks is proportional to the loading rate; the microcrack-strain curves can be divided into three stages: no crack initiation, rapid crack growth and stable crack number; the failure process of the sample is divided into four stages: compaction, elastic deformation, plastic failure and residual deformation; the particles on both sides of the microcrack of the sample have different forms of combined failure, including tensile failure, shear failure and mixed failure of tensile and shear action.