Abstract: This study utilizes a binary mixture of cubic boron nitride (cBN) powders with grain sizes of 1–2 μm and 4–6 μm as the raw material, bonded with Al–Co–TiN, to fabricate polycrystalline cubic boron nitride (PcBN) via a high-pressure, high-temperature (HPHT) process. The influence of the cBN content on the resulting microstructure and mechanical properties was systematically investigated. Experimental results indicate that, across all tested cBN contents, the samples exhibit a consistent phase composition primarily comprising cBN, TiN, AlN, TiB?, and CoN. As the cBN content increases, the relative density of the PcBN composites improves progressively. Optimal mechanical performance in terms of relative density, flexural strength, and fracture toughness was achieved at a cBN content of 70%, reaching values of 99.2%, 567 MPa, and 6.93 MPa·m1/2, respectively. Conversely, at a cBN content of 80%, the PcBN demonstrated the highest microhardness and wear resistance, with values of 43.25 GPa and a specific wear rate of 7325, respectively.