Epidermal growth factor receptor 2 (HER2) is an oncogene involved in tumour genesis and progression. It is expressed in 7% of patients with colorectal cancer (CRC) and is associated with drug resistance of epidermal growth factor receptor monoclonal antibodies. With the emergence of the therapeutic dilemma of CRC and the survival benefits of targeting HER2 for patients with breast cancer and gastric cancer, the significance of HER2 in CRC and the prognostic value of anti-HER2 therapy have been widely concerned, clinical researches on HER2-positive CRC have been continuously carried out. Currently, the diagnostic criteria for HER2 positive CRC have gradually been unified. HER2-targeting therapies such as monoclonal antibodies, tyrosine kinase inhibitors, antibody-drug coupling and HER2-related immunotherapy alone or in combination have shown good efficacy and brought significant survival benefits for HER2 positive CRC. This paper reviews the research progress of HER2 in CRC.