Immune checkpoint inhibitors in the treatment of head and neck squamous cell carcinoma (HNSCC) has shown significant clinical benefit. Some studies have shown that radiotherapy combined with immunotherapy can produce synergistic effects, and several phase Ⅰ/Ⅱ clinical trials have suggested that radiotherapy combined with immunotherapy has good safety and preliminary efficacy benefits in locally advanced HNSCC. However, the timing of combination therapy, the selection of radiotherapy dose/fractionation mode and patients are still unclear. This article further discusses the synergistic mechanism, clinical research status and challenges of radiotherapy combined with immunotherapy in the treatment of HNSCC, aiming to guide the clinical practice and improve the prognosis of HNSCC patients.