Background <p>We aim to explore the preoperative swallowing function of head and neck cancer (HNC) patients, analyze the physiological functions of the oropharyngeal structures during swallowing. Moreover, we conducted a detailed analysis of risk factors that may contribute to impairment in preoperative swallowing function, providing evidence-based support for subsequent tumor treatment and swallowing rehabilitation.</p> Methods <p>This study recruited 107 preoperative patients with HNC from September 2022 to January 2024 in the Hospital of Stomatology, Sun Yat-Sen University. The gold standard fiberoptic endoscopic evaluation of swallowing (FEES) was used to assess swallowing function, primarily encompassing the examination of anatomical structures, pharyngeal secretions, the penetration-aspiration scale, and residue during feeding evaluation. Furthermore, clinical data were collected and we performed univariate and multivariable analyses to identify risk factors of preoperative swallowing function impairment.</p> Results <p>The FEES examination revealed that the capability to retract the tongue root declined in preoperative patients with HNC. And the secretions in the vallecula and piriform sinus increased. During the feeding evaluation, residual boluses in the epiglottic vallecula and piriform sinus increased. The risk of leakage and aspiration has escalated, indicating a significant decline in swallowing function during the pharyngeal phase. In univariate and multivariable analyses, a history of radiotherapy, smoking, and alcoholism are risk factors for the decline in swallowing function.</p> Conclusions <p>Preoperative patients with HNC experience a decline in swallowing function, as evidenced by compromised safety and effectiveness of swallowing.</p>