Depressive disorder is currently the disease with high risk of suicide， seriously threatening the physical and mental health of people of all ages， and causing a huge burden on patients' families and society. There are differences in brain structure and function between patients with depressive disorder and healthy individuals. The neuroimaging features of the hippocampus are becoming important biomarkers for diagnosing depressive disorder and predicting its progression， providing a new reference for early diagnosis and treatment of depressive disorder. This paper reviews the research status of the structure and function of the hippocampus in patients with first-episode depressive disorder， and explores in detail the changes in the structure and function of hippocampus， aiming to provide accurate and efficient reference for screening， diagnosis， and treatment of first-episode depressive disorder patients using magnetic resonance imaging as a non-invasive examination method.