Abstract: The low axial compressive strength and complex failure mechanisms of high-modulus carbon fiber reinforced polymer (HMCFRP) composites limit their application potential in aerospace fields with higher performance demands. To reveal the underlying microscopic failure mechanisms, a micromechanical finite element model incorporating random fiber strength distribution was developed. This model couples the fiber Hashin damage criterion and the resin plastic failure criterion, enabling simulation of the entire process from damage initiation to final failure under axial compression. The simulation results indicate that the properties of the resin matrix dominate the compressive failure path. When the resin tensile strength exceeds 100 MPa and its modulus exceeds 4.0 GPa, the system exhibits “interface-dominated failure”, characterized by extensive interfacial debonding leading to cooperative fiber buckling. Conversely, when the resin properties are below these thresholds, the system demonstrates “resin-dominated failure”, triggered by resin plastic deformation and progressive debonding. A parametric study was conducted to quantify the influence weight of each constituent’s properties. It was found that resin strength is the most critical factor determining the final compressive strength, with its influence weight approaching 30%. This research clarifies the microscopic failure mechanisms and decisive factors for the compressive failure of HMCFRP, providing a theoretical basis for the targeted optimization of resin matrix properties to fully exploit the potential of high-modulus carbon fibers.