Objective:To investigate the chronic function damage of the salivary gland by high dose of 131I in the treatment of differentiated thyroid carcinoma(DTC). Methods:Salivary gland scintigraphy,for function evaluation,were made before and 6~39 months after high dose of 131I treatment on 143 patients with DTC after thyroid ablation. Results:21.7%(31/143)patients with DTC suffered from chronic salivary gland damage after 131I treatment. And the incidence of chromic damage was more predominant in patients received repeated 131I therapy(aggregated dose ranging from 7.4~37.0 GBq)than those treated with once 131I therapy(dose less than 3.7 GBq).(P < 0.005). Conclusion:Repeating and large dose of 131I treatment is more common in the causes of chronic salivary gland damage.