To investigate the influence of the crack angle on the strength and energy evolution of granite-concrete composite specimens under uniaxial compression, a numerical simulation study was conducted using the two-dimensional particle flow code (PFC^2D) based on the micro-parameters calibrated through laboratory tests. The research results indicate that the strength and deformation characteristics of granite-concrete are affected by crack angles, and their strength and deformation parameters gradually increase with the increase of crack angle. During the uniaxial compression process, the internal energy of the specimens transforms into macroscopic crack propagation, and the final failure modes are mainly tensile fractures and shear fractures. The total energy and dissipated energy of the composite specimens increase with the increase of crack angle, and the total strain energy is more than the dissipated energy when the specimens are damaged. Based on the calculation of dissipated energy, a damage constitutive equation was constructed, indicating that when the damage factor reaches 0.8, the specimen is already close to its limit state, resulting in significant energy consumption and a decrease in the strength of the composite specimen.