Objective:To investigate the effect of microRNA-124 (miR-124) expression on pathological changes of Tau in elderly patients with Alzheimer disease to provide a new target for early detection and early treatment of Alzheimer disease in the elderly.Methods:The serum of 50 patients with Alzheimer disease from June 2017 to June 2018 in the Third People′s Hospital of Qinghai Province Hospital was taken as the sample of the research group and the serum of 50 healthy people was taken as the control sample. The mRNA expression of miR-124 in serum was determined by real-time polymerase chain reaction. The double antibody sandwich enzyme-linked immunosorbent assay was used. The expression levels of Tau protein and phosphorylated Tau (PTau) protein (S396, T181 and T231) were examined; pathological changes of Tau protein were detected by positron emission tomography.Results:The mRNA expression of serum miR-124 in Alzheimer disease patients was significantly higher than that in the control group (6.91 ± 0.41 vs. 5.11 ± 0.37, P < 0.01). The expression levels of total Tau protein, PTau (S396) protein and PTau (T181) protein in Alzheimer disease patients was significantly up-regulated, compared with those of the control group: (195.16 ± 20.48) ng/L vs. (123.25 ± 20.26) ng/L, (69.35 ± 8.92) ng/L vs. (40.53 ± 4.36) ng/L, (66.83 ± 8.45) ng/L vs. (35.87 ± 2.18) ng/L, P < 0.05. The pathological changes of Tau protein were clinically manifested as brain deposition, and the main parts were frontal lobe, occipital lobe, parietal lobe and temporal lobe. The overexpression of miR-124 was positively correlated with high expression of PTau (S396), high expression of PTau (T181) and high expression of total Tau, and it was an independent influencing factor. Conclusions:Overexpression of miR-124 can promote the expression of total Tau protein and phosphorylation of Tau protein, which is clinically indicative of Tau protein deposition in the brain of Alzheimer disease patients. It is expected to be a prognostic biomarker for Alzheimer disease.