Background: APOE4 have been considered as the risk of AD, but the predict value of MCI progressing to AD was not clear. Objective:The aim of the current study was to investigate the predictive-value of APOE4+ in the development of Mild Cognitive Impairment (MCI) to Alzheimer's Disease (AD) using a meta-analysis.Methods: At PubMed, Elsevier Science Direct, Scihub and Google Scholar we searched all the previous cohort studies on APOE4+ genotype associated with the risk of MCI-to-AD dementia, published before January 1, 2019. Stata Meta-DiSc (version 1.4) software was used to pool the APOE4+ prognosis data to examine the sensitivity, specificity and the summary receiver operating characteristic curve (SROC) in predicting the risk MCI-to-AD dementia; Stata software, to calculate the relative risk (RR) and 95% CIs.Results: For the meta-analysis were involved 43 previously reported studies, where it was found that in MCI people aged ≥70, who had progressed to AD dementia within 5 years, the APOE4+ predictive sensitivity was 0.71; the specificity, 0.71; and AUC, 0.78. Moreover, the results showed that RR was 1.49 and 1.56, respectively, for MCI people in general and for MCI people aged ≥70 and with the risk of APOE4+-to-AD. Particularly, the RR was 2.24 for the individuals aged ≥70 and with APOE4+ who progressed to AD dementia within 5 years. Conclusion:The findings strongly suggested that it could take less than 5 years for MCI people aged ≥70 and with the gene of APOE4 to progress to AD dementia.