Objective To explore the relationship of blood pressure variability and cognitive impairment in the very elderly patients with hypertension. Methods A total of 177 hypertensive patients (80-91 years old) admitted in our department from March to December 2017 were recruited in this study. According to the results of Montreal cognitive assessment (MoCA), the patients were divided into mild cognitive impairment group (MCI group, n=114) and normal cognitive group (control group, n=63). The general conditions, laboratory examination results, mean blood pressure, variable coefficient and circadian rhythms of blood pressure, and morning surge in blood pressure were compared between the 2 groups. SPSS statistics 17.0 was used to perform the statistical analysis. Student＇s test or Chi-square was employed for comparison between two groups. Results There were no significant differences in general conditions between the 2 groups (P>0.05). The patients from MCI group had obviously higher variable coefficient of systolic blood pressure [(0.11±0.02)% vs (0.08±0.03)%, P<0.05] and diastolic blood pressure [(0.12±0.02)% vs (0.11±0.03)%, P<0.05] than those in the control group. No significant differences were seen in declined rate of systolic blood pressure and diastolic blood pressure and morning diastolic blood pressure surge between the 2 groups (P＞0.05). The morning systolic blood pressure surge was also significantly higher in the MCI group than the control group [(17.37±5.36) vs (13.60±3.57) mmHg, P<0.05]. No significant differences were seen in the ratios of patients presenting non-dipper type, dipper type, reverse dipper type and over dipper type of blood pressure between the 2 groups(P＞0.05). Conclusion Controlling blood pressure variability and morning systolic blood pressure surge is helpful to the improvement of cognitive function in very elderly hypertensive patients.