To address the issues of lack-of-fusion defects and performance degradation caused by the high laser reflectivity and thermal conductivity of pure copper during laser powder bed fusion (L-PBF) additive manufacturing, this study proposes constructing copper matrix composites by incorporating submicron tungsten carbide (WC) particles. The influence mechanisms of WC content (mass fraction of 1% and 3%) on microstructure and mechanical properties were systematically investigated. The results show that WC particles significantly enhanced the laser absorptivity of composite powders. The mass fraction of 3% WC-doped copper specimen achieved densification with elimination of lack-of-fusion defects, while the average grain size increased from 11.4 μm (pure copper) to 22.8 μm, accompanied by the formation of a preferred <110> orientation texture. Transmission electron microscopy (TEM) analysis revealed a 34 nm elemental transition zone at the interface between WC particle and Cu matrix, and the formation of a new phase (CuWO₄). Tensile tests indicated that the mass fraction of 3% WC-doped copper specimen exhibited an ultimate tensile strength of (229±2) MPa and elongation of (41.6±1.6)%, representing 77.5% and 161.6% enhancements compared to pure copper (129±2) MPa, (15.9±0.6)%, respectively. Fracture surfaces displayed typical dimple characteristics. This study provides a theoretical basis for laser additive manufacturing of high-density, high-performance copper matrix composites.