To evaluate the diagnostic value of apolipoprotein E (APOE) gene in Alzheimer's disease (AD). Databases including PubMed, EMBASE, Google Scholar, Wanfang Med online, China National Knowledge Infrastructure (CNKI), and China Biomedical Literature Database (CBM) were searched for literatures in English or Chinese. No limitations on the date. The sensitivity, specificity, likelihood ratio, and diagnostic odds ratio were pooled for meta-analysis. The symmetric receiver operator characteristic curve (SROC) and Fagan's Nomogram were drawn, and metaregression and subgroup analysis were used to explore the source of heterogeneity. A total of 13 studies, including 2662 cases and 8843 controls, were analyzed. The combined sensitivity (SEN) was 0.62 (95% CI (0.58-0.66)), specificity (SPE) was 0.84 (95% CI (0.81-0.86)), the positive likelihood ratio was 3.8 (95% CI (3.3-4.3)), and the negative likelihood ratio was 0.45 (95% CI (0.41-0.49)). The area under the ROC curve was 0.80, and the diagnostic ratio (DOR) was 8. Neither publication bias was detected in Deeks' funnel plot, nor threshold effect was shown in the SROC. Metaregression analysis showed that the diagnostic methods, experimental design, and sample size contributed to the heterogeneity in SEN, while the diagnostic methods, experimental design, blind evaluation on test results, and sample size contributed to the heterogeneity in SPE. When the pretest probability was set as 50%, the posterior probability in Fagan's Nomogram was 79%, the positive likelihood ratio (LRP) was 5, and the negative likelihood ratio (LRN) was 0.42. AD could neither be confirmed nor excluded by the APOE genotype test. The sensitivity and specificity of the APOE gene test were relatively low in the diagnosis of AD. The diagnostic value of APOE ε4 gene in AD was moderate; it might play an important role in the prevention of AD. Copyright © 2020 Xuan Xiong et al.