Objective To compare different beginning time of acid simulation to reduce the acute damage of salivary glands after high-dose of iodine-131 treatment for the post-surgery patient with differentiated thyroid cancer (DTC) and screen out the optimal beginning time of acid simulation .Methods Total 309 cases of post-surgery DTC patients accept high-does ioding-131 treatment (average dose of ioding-131 :4 .28 ± 0 .43 GBq) ,and all patients was divided into three group randomly ,the beginning time of acid stimulation(vitamin C :10 mg per time ,three time a day ,lemonade:50 mL per 2 h) for each group is 2 ,12 and 24 h .Then observe the incidence and time of acute damage of salivary glands for each group .At same time ,we analyses the relation between acute dam-age of salivary glands with sex and age .Results The incidence of acute damage of salivary glands is 13 .21% (2 h) ,24 .51% (12 h) , 26 .73% (24 h)respectively ,the incidence of 2 h is lower than those of 12 h and 24 h obviously(P<0 .05) ,and there is no difference between 12 h and 24 h(P>0 .05) .The occurrence time of acute damage of salivary glands for 84 .85% patients is between 10-24 h .And there is no difference of incidence of acute damage of salivary glands between different sex and age group .Conclusion 2 h maybe the optimal beginning time of acid simulation to reduce the acute damage salivary glands for the post-surgery DTC patients after high-dose iodine-131 treatment in this study .Sex and age are no influence to the occurrence of acute damage of salivary glands .