Alzheimer′s disease (AD) and cerebral amyloid angiopathy (CAA) have close clinical and pathological relationships. In this paper, a 54-year male patients with AD and CAA is reported. AD is diagnosed according to A/T/N biomarker framework, and the clinical diagnosis of CAA is based on Boston Diagnostic criteria 2.0. So far, it has not been reported in China. At the same time, the abnormal changes of β-amyloid protein (Aβ) in this case were confirmed by cerebrospinal fluid detection and neuromolecular imaging. Finally, through the review of the literature, it is expounded that the deposition of Aβ is the common pathology of CAA and AD, leading to cognitive dysfunction and neurological dysfunction. For CAA, the major event in the pathogenesis is vascular Aβ deposition, while for AD is inflammatory plaque Aβ deposition in the brain. The pathological changes of both are driven by Aβ clearance disorders. However, mechanisms of brain injury between them were different. The mechanism of AD-related brain injury is mainly related to synaptic and neuron loss caused by Aβ deposition, while CAA-related brain injury is more likely to be caused by vascular dysfunction, vascular integrity damage, hemorrhage or cerebral hypoperfusion. Since obvious clinical heterogeneity in AD, for patients with AD and without intracerebral hemorrhage, routine screening magnetic sensitivity weighted imaging scanning is needed to exclude CAA.