Abstract Objective: To analyze the value of serum miRNA-122 expression in the diagnosis, severity, and prognosis of Acute Cerebral Infarction (ACI) and the correlation mechanism of serum miRNA-122 on the proliferation and apoptosis of vascular endothelial cells in ACI. Method: A total of 60 patients with ACI who were admitted to the emergency department of the Taizhou People’s Hospital from January 1, 2019, to December 30, 2019, and 30 healthy controls during the same period were selected. General clinical data of all patients at admission were collected. Including age, sex, medical history, and inflammatory factors (C-Reactive Protein [CRP], Interleukin-6 [IL-6], Procalcitonin [PCT], Neutrophil Gelatinase-Associated Lipid carrier protein [NGAL]). The National Institutes of Health Stroke Scale (NIHSS) score at admission and short-term prognosis (the Modified Rankin Score [mRS]) score at 3 months after onset were recorded. The expression level of miRNA-122 in the serum of patients with ACI and normal controls was detected by reverse-transcription quantitative Real-Time Polymerase Chain Reaction (RT-QPCR), and the correlation between the expression level of miRNA-122 in the serum of patients with ACI and the level of inflammatory factors, NIHSS and mRS scores were analyzed. The expression levels of miRNA-122 in the serum of patients with ACI, normal people, and Human Umbilical cord Endothelial Cells (HUVECs) cultured in a blank control group were detected by RT-QPCR and statistically analyzed. MTT and flow cytometry was used to compare the proliferation and apoptosis of vascular endothelial cells in the miRNA-122 mimics and inhibitors transfection groups and the corresponding negative control group. The mRNA and protein levels of apoptosis-related factors Bax, Bcl-2, Caspase-3, and angiogenesis-related proteins Hes1, Notch1, Vascular Endothelial Growth Factors (VEGF), and CCNG1 were detected by RT-QPCR and Western blot. Bioinformatics methods predicted CCNG1 to be the target of miRNA-122, and the direct targeting relationship between CCNG1 and miRNA-122 was verified by a dual-luciferase reporting assay. Result: Serum miRNA-122 expression in patients with ACI was significantly higher than that in healthy controls, with an area under the receiver operating characteristic curve of 0.929, 95% Confidence Interval of 0.875‒0.983, and an optimal cut-off value of 1.397. The expression levels of CRP, IL-6, and NGAL in patients with ACI were higher than those in healthy control groups, p < 0.05; miRNA-122 was positively correlated with CPR, IL-6, NIHSS score, and mRS score. At 48h and 72h, the proliferation rate of HUVECs cells in the miRNA-122 mimics group decreased and the apoptosis rate increased. Cell proliferation rate increased, and apoptosis rate decreased significantly in the groups transfected with miRNA-122 inhibitors. The mRNA and protein levels of pro-apoptotic factors Bax and caspase-3 were significantly increased in the miRNA-122 mimics transfection group, while those of anti-apoptotic factor Bcl-2 were significantly decreased compared to those of the control group. The expression of Bax and Caspase-3 decreased, and the expression of anti-apoptotic factor Bcl-2 increased in the transfected miRNA-122 inhibitors group. mRNA expression levels of Hes1, Notch1, VEGF, and CCNG1 in the miRNA-122 mimic transfected group were significantly decreased, while mRNA expression levels in the miRNA-122 inhibitors transfected group were significantly increased. Bioinformatics showed that there was a miRNA-122 binding site in the 3′UTR region of CCNG1, and dual luciferase assay confirmed that CCNG1 was the target of miRNA-122. Objective miRNA122 miRNA 122 miRNA-12 diagnosis severity (ACI Method 6 Peoples People s 1 2019 selected collected age sex history CReactive C Reactive CRP , [CRP] Interleukin6 Interleukin Interleukin- IL6, IL6 IL [IL-6] PCT, PCT [PCT] GelatinaseAssociated Gelatinase Associated NGAL. . [NGAL]) (NIHSS shortterm short term [mRS] recorded reversetranscription reverse transcription RealTime Real Time RTQPCR, RTQPCR RT QPCR (RT-QPCR) analyzed people (HUVECs apoptosisrelated related Bcl2, Bcl2 Bcl 2, 2 Caspase3, Caspase3 Caspase 3, angiogenesisrelated angiogenesis Hes1 Hes Notch1 Notch VEGF (VEGF) CCNG blot miRNA122, 122, dualluciferase Result 0929 0 929 0.929 95 08750983 875 983 0.875‒0.983 cutoff cut off 1397 397 1.397 6, IL-6 0.05 005 05 CPR h 72h proapoptotic pro apoptotic caspase3 caspase caspase- antiapoptotic anti Bcl- Caspase- 3UTR UTR miRNA122. 122. miRNA12 12 miRNA-1 201 [CRP [IL-6 [PCT [NGAL] [mRS (RT-QPCR (VEGF 092 92 0.92 9 0875098 87 98 0.875‒0.98 139 39 1.39 IL- 0.0 00 miRNA1 miRNA- 20 [IL- [NGAL 09 0.9 087509 8 0.875‒0.9 13 1.3 0. [IL 08750 0.875‒0. 1. 0875 0.875‒0 087 0.875‒ 08 0.875 0.87 0.8