Head and neck cancer is one of the common malignant tumors, and most patients are diagnosed in the middle and late stages of the disease. Therefore, early diagnosis, accurate staging and efficacy monitoring are the key to optimize the treatment strategy and improve the prognosis of head and neck cancer. Integrated PET/MRI integrates molecular function and anatomical structure imaging to achieve the advantages of PET and MRI. Combining the metabolic information of PET with the good soft tissue contrast of MRI to realize multimodal imaging has important clinical significance in the diagnosis and treatment of tumors. This review focuses on the application and progress of PET/MRI in the diagnosis, staging, monitoring treatment response, predicting prognosis and radiotherapy planning of head and neck cancer.