A large number of patients undergoing radiotherapy and chemotherapy are suffering from dry mouth. Due to reduced saliva secretion, patients may experience symptoms such as difficulty chewing and swallowing. In severe cases, they may also experience pain and burning sensation in the oral mucosa, decreased taste, ulcers, which seriously affect the quality of life of patients. However, radiation-induced dry mouth lacks early objective predictive indicators (molecular biomarkers) and the mechanism is unclear. Only when patients experience clinical symptoms will symptomatic treatment be taken to alleviate them. Therefore, elucidating the mechanism of radiation-induced dry mouth syndrome (RIX) and achieving early prediction, detection, and intervention of RIX are crucial in improving the prognosis and quality of life of radiotherapy patients. It is urgent to seek early and precise detection targets in clinical practice to predict dry mouth caused by irreversible damage to salivary gland tissue. This study aims to collect blood samples from patients with severe dry mouth before and after radiotherapy and chemotherapy in clinical practice. Multiple omics techniques will be used to search for predictive molecular biomarkers for RIX, construct a predictive model, and verify the sensitivity and specificity of the biomarkers. The goal is to predict the occurrence of RIX early in clinical practice, intervene in advance, greatly improve the prognosis of radiotherapy and chemotherapy patients, and enhance their quality of life.