Abstract: Radiotherapy is the main treatment for head and neck cancer, but it will result in adjacent tissue damage,including radioactive xerostomia,the most common complication.The mechanism of radiationinduced parotid damage injury is unclear. Parotid function test include detection of parotid salivary flow and salivary flow rate, parotid SPECT, CT and MRI, etc.How to protect the parotid glands becomes a hot research in recent years.At present,the main methods of protecting the parotid glands includes selecting patterns of radiotherapy,radiotherapy planning optimization,drugs，stem cell transplantation and gene transduction.