High-flow nasal cannula (HFNC) has emerged as a promising tool for enhancing patient safety during the induction of general anesthesia. Its ability to deliver heated and humidified high-concentration oxygen demonstrates significant potential for prolonging the safe apnea time and improving oxygenation, particularly in patients at a high risk of rapid desaturation. This review assesses the efficacy of HFNC across diverse patient populations, focusing on its utility in managing difficult airways and facilitating rapid sequence intubation. A systematic literature search was performed to identify relevant clinical studies, including randomized controlled trials (RCTs) and observational studies. The synthesized evidence robustly confirms that HFNC provides a superior extension of the duration of safe apnea compared to conventional oxygen therapy methods. The underlying physiological mechanisms are thoroughly discussed, primarily centering on pharyngeal dead space washout and the generation of a mild positive pharyngeal pressure, which collectively enhance alveolar oxygen reserves. Moreover, clinical data indicate that HFNC reduces the incidence of critical desaturation events across diverse patient populations and clinical scenarios. Nonetheless, the analysis also highlights a significant heterogeneity in study designs, patient cohorts, and intervention protocols among the available research. Crucially, data concerning long-term safety outcomes and precisely optimized application strategies tailored to different patient risk profiles remain scarce. In conclusion, HFNC represents a physiologically rational and highly effective technique for increasing the safety margin during the critical phase of anesthesia induction. To firmly integrate HFNC into routine clinical practice, future research must prioritize large-scale, high-quality RCTs to validate long-term benefits, define evidence-based standardized application guidelines, and identify the most suitable patient cohorts for HFNC.