Trastuzumab is a monoclonal antibody directed against the human epidermal growth factor receptor-2( HER-2). Recent studies found that Trastuzumab in combination with chemotherapy could improve the survival of patients with HER-2 positive advanced gastric. However, the use of techniques like immunohistochemistry, fluorescence in situ hybridization (FISH) in assessing HER-2 status of gastric cancer has many disadvantages, a new technique silver-enhanced in situ hybridization (SISH) is likely to be the reference standard for assessing HER-2 status of gastric cancer. This paper reviews the advance of the detection and clinical studies of HER-2 in gastric cancer.