Abstract: Alzheimer disease (AD) is one of the most common progressive neurodegenerative diseases, which seriously threatens the life and health of patients. Early diagnosis and intervention can slow down or even reverse the progression of the disease. At present, MRI and PET imaging have been applied in the diagnosis of AD, which have unique advantages in the early diagnosis of AD. The authors focus on the application of structural MRI, functional MRI and PET imaging in the early diagnosis of AD.