Abstract Objective: To investigate the relationship between miR-132-3p level in circulating blood and the degree of cognitive impairment and hippocampal atrophy in Alzheimer's disease (AD) patients, as well as its diagnostic value. Methods: The expression level of miR-132-3p in brain tissue between early and late AD patients and between AD patients and normal subjects was verified using GEO datasets. By collecting blood samples and various data from AD patients and normal subjects, the changes of miR-132-3p in blood in AD were analyzed. A total of 50 AD patients and 50 healthy individuals were recruited from the Memory Clinic of the Neurology Department of the Affiliated Hospital of Binzhou Medical College between January 2021 and January 2023. All patients underwent cognitive function tests and MRIs. The height of the hippocampus and the width of the temporal horn were measured linearly, and the volume of the hippocampus was calculated using the MTA visual score system. RT-PCR was used to detect the expression levels ofmiR-132-3p in patient blood. Pearson and Spearman correlation coefficient were used for correlation analysis. Finally, the miRNA target gene of Alzheimer's disease was predicted through a cross-analysis using the miRDB and TargetScan prediction websites, as well as the SE29378 dataset from GEO. Results: 1. According to the data analysis, miR-132-3p in the prefrontal cortex was significantly decreased in the late AD period (p<0.001). The expression of miR-132-3p in the temporal cortex and cerebrospinal fluid of AD patients exhibited a decreasing trend compared to that of healthy individuals. 2. MiR-132-3p expression level in the blood of AD patients was significantly lower compared with that of healthy individuals (p<0.001). 3. The hippocampal height, MMSE score, and MoCA score were significantly lower while temporal horn width and MTA score were significantly higher in AD patients than in healthy individuals (p＜0.001). 4. MiR-132-3p expression in blood was positively correlated with MMSE score, MoCA score, and hippocampal height (rMMSE2=0.5067, rMoCA2=0.6101, rHippocampal height2 =0.6686; p<0.001), but negatively correlated with MTA score and temporal horn width (rMTA score2 =0.1699, rTemporal Angle width2 =0.2922; p<0.001). 5. ROC curve analysis revealed that when the optimal cut-off value was 0.6944, the area under the curve of blood miR-132-3p expression, sensitivity and specificity values for AD diagnosis were 0.7640, 74.00%, and 70.00%, respectively. 6. By integrating the three datasets and conducting cross-analysis, we identified two genes, BRI3 and SPTSSA, as the targets of miRNA involved in AD. Conclusion: The expression of miR-132-3p in all brain regions of AD patients exhibited a significant decrease, with lower levels observed in the late stage compared to the early stage of the disease. Experimental detection also revealed a significant reduction in miR-132-3p expression in the blood of AD patients, which correlated with hippocampus atrophy and cognitive function assessed by brain MRI. It is suggested that blood miR-132-3p levels could serve as a potential clinical diagnostic indicator. Cross-analysis of gene data sets indicates that BRI3 and SPTSSA may be target genes through which miR-132-3p affects AD.