Abstract: ob＜x＞jective To observe the ability of cog-12 scale combined with apolipoprotein E genotyping to detect mild cognitive impairment (MCI) in elderly people over 65 years old.Methods 31 cases in the control group, 29 cases in the MCI group and 27 cases in the alzheimer’s disease (AD) group were selected according to their cognitive level.Each group completed cog-12, ROSA, MoCA, MMSE and apoliprotein E genotyping.Results Compared with the control group (2.6±1.4), the cog-12 score of MCI group (9.1±4.2) and AD group (22.5±7.2) was significantly increased (P< 0.05).The co-aging of ROSA, MoCA and MMSE was -0.844, -0.897 and -0.881, respectively.The diagnostic sensitivity and specificity of MCI were 76.5%, 90.2%, and 0.875 respectively.The most common ApoE genotypes in the control group, the MCI group and the AD group were epsilon 3, epsilon 4 and epsilon 4 genotypes, with statistically significant differences (P<0.05).Conclusion Cog-12 is a simple and effective screening tool for cognitive function, and the two types of gene are most common in patients with MCI and AD. The combined detection of the two can effectively detect MCI patients in the elderly population, so as to better evaluate the risk factors of dementia and disease progression.