Oral cancer is a common malignant tumor in head and neck cancers, and the metastasis of cervical lymph nodes directly affects the prognosis of patients with oral cancer. Exploration and study on the detection of occult lymph nodes in patients with negative cervical lymph nodes is of great importance to improve the prognosis of patients with early oral cancer. This article reviews some progresses of occult lymph node metastasis of oral cancer in ultrasound guided fine-needle aspiration cytology (US-FNAC)、positron emission tomography and single-photon emission computed tomography/computed tomography (SPECT/CT) fusion technology, sentinel lymph node biopsy technique (SLNB) and molecular biological detection、nanotechnology and quantum dot technology.