Objective To explore the application value of MR diffusion weighted imaging(DWI)and T2*mapping of parotid gland function in patients with head and neck tumors at different radiotherapy periods.Methods A total of 82 patients with head and neck tumors treated were selected.The data of parotid gland volume,salivary volume and parotid gland function were collected.MR DWI and T2*mapping were used to measure the apparent diffusion coefficient(ADC)value and T2*value of parotid gland tissue,and the correlation between parotid gland function and imaging values were analyzed.Results There were all significant differences in parotid gland volume,salivary volume and secretion index among different radiotherapy periods,and parotid gland volume,salivary volume and secretion index during and after radiotherapy were significantly lower than those before radiotherapy.There were signifi-cant differences in T2*values among different radiotherapy periods,and T2*value during and after radiotherapy was significantly lower than that before radiotherapy.There were significant differences in ADC values among different radiotherapy periods,and the ADC value during and after radiotherapy was significantly higher than that before radiotherapy.ADC value was negatively correlated with parotid gland volume,salivary volume and secretion index(r=-0.436,-0.730,-0.718,respectively,P＜0.001),while the T2*value was positively correlated with parotid gland volume,salivary volume and secretion index(r=0.430,0.720,0.707,respec-tively,P＜0.001).Conclusion Parotid gland volume,secretion index and salivary volume show abnormal levels at different radio-therapy periods.MR DWI is negatively correlated with parotid gland function,while T2*mapping is positively correlated with parotid gland function.