Both unipolar depression (UD) and bipolar depression (BD) have obvious depression symptoms.Clinically,UD and BD are often misdiagnosed.Recently,MR imaging (MRI) has been used to detect biomarkers distinguishing BD and UD.This study will summarize previous studies on detecting biomarkers to distinguish BD and UD based on structural MRI,diffusion tensor imaging (DTI) and functional MRI.Based on the current issues of previous studies,we further make prospective development of future studies in this field.