In order to improve the mechanical properties of nano hydroxyapatite (HA), silicon carbide whisker (SiC_w) with excellent mechanical and biological properties was used as the reinforcement for SiC whisker reinforced nano hydroxyapatite (SiC_w/HA) composites. Hydrothermal synthesis method was adopted to prepare the uniformly dispersed SiC_w and HA composite powders, and SiC_w/HA composites were fabricated by pressureless sintering. The interfacial bonding state and mechanical properties of SiC_w/HA composites in different sintering atmospheres (air and N₂) were systematically investigated. The results show that the uniformity of the composite powders decreases with the increase of SiC_w content, and the cross-section of SiC_w/HA composites gradually changes from glossy and smooth to rough and undulate. When the content of SiC_w is 15 wt%, the maximum bending strength and fracture toughness of the composites sintered in air atmosphere (HAW15) are 40.85 MPa and 1.82 MPa·m^1/2 respectively, which are higher than those of pure HA. Compared with those of the SiC_w/HA composites sintered in N₂ atmosphere, the bending strength and fracture toughness of the HAW15 composites are increased by 154.2% and 10.3%, respectively. Moreover, Simulated body fluid (SBF) and in vitro cell behavior tests indicate that the SiC_w/HA composites still have excellent bioactivity. The possible strengthening and toughening mechanisms of SiC_w/HA composites are that the dispersion of SiC_w in HA matrix is improved by hydrothermal process, and the interfacial bonding property is enhanced because of the reaction fusion on interface of SiC_w/HA composites during sintering in air atmosphere. The adoption of hydrothermal process improves the dispersion uniformity of SiC_w in HA matrix. When sintering in air atmosphere, the interfacial bonding property of SiC_w/HA composite is enhanced via the reaction fusion (SiO₂ is formed by the oxidation of SiC_w). Both of them lead to the increase of strength and toughness of the composites. This study would provide additional insights into the feasibility of SiC_w/HA composites as load-bearing implant materials in orthopedic applications.