Silicon nitride (Si₃N₄) bioceramics exhibit promising potential in bone tissue engineering and implant materials due to their outstanding mechanical properties, biocompatibility, bioactivity, and remarkable antibacterial characteristics. This review systematically summarizes the crystalline phase structure, microstructure, and surface chemical properties of silicon nitride ceramics. It discusses the effects of grain size, grain boundary characteristics, and sintering processes on mechanical strength and toughness, as well as the mechanisms through which surface oxidation and hydrolysis release bioactive compounds such as silicates and ammonia, promoting osteogenesis and inhibiting pathogens. Moreover, composite materials of silicon nitride with graphene, silicon carbide whiskers, and other nanomaterials have significantly improved mechanical performance and have been successfully applied in spinal fusion, hip joint replacement, and dental restoration, demonstrating superior osseointegration, low wear, and excellent antimicrobial effects. However, inherent brittleness and slow degradation rates still limit wider clinical applications. Future research should focus on developing novel silicon nitride composites with graphene and carbon nanotubes to precisely regulate degradation rates, employing artificial intelligence to optimize sintering processes for accurate microstructural control, and conducting multicenter clinical trials to comprehensively evaluate long-term safety and effectiveness, thereby offering more efficient, safe, and reliable solutions for bone defect repair and regenerative medicine.