Objective To investigate the correlation between serum 1,5-anhydroglucitol (1,5-AG) and mild cognitive impairment (MCI). Methods According to the diagnostic criteria of MCI and the cognitive function test results by Montreal cognitive assessment (MoCA) scale Chinese version, 80 volunteers receiving health check in our hospital from Nov. to Dec., 2019 were divided into MCI group (33 cases) and normal control (NC) group (47 cases). The demographic and clinical data were collected, and the blood glucose-related indexes, including 1,5-AG, fasting plasma glucose (FPG), glycosylated hemoglobin (HbA1c) and 2 h-postprandial glucose (2 h-PPG), were measured. Anxiety and depression were assessed by self-rating anxiety scale (SAS) and geriatric depression scale (GDS), respectively. Linear correlation analysis and multiple linear regression analysis were used to study the correlation between the blood glucose-related indexes and MCI. Results There were no significant differences in the demographic data, clinical data, SAS score or GDS score between the two groups (all P> 0.05). Compared with the NC group, the MoCA score and the level of 1,5-AG were significantly lower in the MCI group (P<0.01, P=0.023), and the levels of FPG and 2 h-PPG were significantly higher (P=0.041, 0.027). Linear correlation analysis showed that the MoCA score was negatively correlated with the levels of FPG, 2 h-PPG and HbA1c (all P<0.05), but not with 1,5-AG level (P=0.134); the score of delayed recall, a cognitive domain of MoCA scale, was negatively correlated with the levels of FPG, 2 h-PPG and HbA1c (all P<0.05), and positively correlated with the 1,5-AG level (P=0.027). Multiple linear regression analysis showed that FPG was an independent factor of MoCA score (β=-0.291, P=0.009), and 1,5-AG and FPG were independent factors of delayed recall score (β=0.199 and -0.390, P=0.015 and 0.001). Conclusion 1,5-AG may be a potential biomarker for predicting cognitive impairment, especially for delayed recall; the blood glucose fluctuates greatly in MCI individuals at early stage, and maintaining the stability of blood glucose may be beneficial to the prevention of MCI.