Abstract: Differentiated thyroid cancer (DTC) is the most common endocrine malignancy, which is prone to lymph node metastasis in the early stage. ¹³¹I whole body scan combining with SPECT/CT (called ¹³¹I SPECT/CT for short) can often detect residual and/or missed lymph node metastasis, which may change the postoperative staging and risk stratification of patients, affect subsequent surgical or ¹³¹I therapy options. ¹³¹I therapy is one of the effect methods for the treatment of postoperative cervical lymph node metastasis in DTC. Metastatic lymph nodes can be diagnosed by ¹³¹I SPECT/CT. This article reviews the application value of ¹³¹I SPECT/CT in the diagnosis and treatment of postoperative lymph node metastasis in patients with differentiated thyroid cancer.