Abstract: Thyroid cancer account approximately 1.3%-1.5% of cancers all over the body, the attack rate is raising up recently. Most operation is subtotal thyroidectomy at the first time, because thyroid cancer was regarded as thyroid nodule usually account 90.5%. Operation one more time with leftover cancer rate about 41.3%, and with lymphonodi cervicales deadexis about 72.8%. Most patient reluctancy operation again in view of complication with hypoparathyroidism and injure of recurrent nerve. The efficacy of radioiodine ablation can eliminate the minimum cancer which concealed in remained thyroid glandular tissue, and cut down the recurrence rate of thyroid cancer, and destroy metastasis, in favour of long-term follow-up. A great quantity of literature report about 60% with 1.11GBq ¹³¹I and 90% with retreatment with 1.11GBq ¹³¹I in patients with differentiated thyroid cancer undergoing subtotal thyroidectomy.¹³¹I treatment can shorten length of stay, and decrease radiation effect, and cut down side effect and economy burden, as far as possible to achieve therapeutic efficacy.