Aim To study correlation between left ventricular hypertrophy (LVH) and index of blood pressure variability(BPV) in patients with hypertension complicated with diabetes mellitus. Methods 120 hypertension patients combined with diabetes mellitus were included, and divided into LVH group and non-LVH group according to their clinical confirmed information and electrocardiographic data. BPV-related indices were compared between the two groups, Logistic regression was used to analyze the risk associated with LVH in patients. Pearson correlation analysis was used to analyze the correlation between left ventricular mass index (LVMI) and BPV. Results In patients with hypertension and diabetes, daytime systolic blood pressure variability coefficient (dSBPCV), daytime diastolic blood pressure variability coefficient (dDBPCV), 24 h systolic blood pressure variaility coefficient (24hSBPCV), and 24 h diastolic blood pressure variability coefficient (24hDBPCV) in LVH group were significantly higher than those in non-LVH group (P＜0.05). Logistic regression analysis showed that the increase of dSBPCV, dDBPCV, 24hDBPCV and 24hSBPCV were related risk factors for LVH in hypertensive patients with diabetes mellitus (OR＞1, P＜0.05). Pearson correlation analysis showed that LVMI was positively correlated with 24hSBPCV, 24hDBPCV, dSBPCV and dDBPCV (r＝0.5,0.2,0.387 and 0.441, P＜0.05). Conclusions BPV in hypertensive patients with diabetes mellitus has a certain effect on left ventricular hypertrophy. BPV can be used as a predictor of target organ damage in hypertensive patients with diabetes mellitus. BPV control has a certain clinical value for early prevention and treatment of left ventricular hypertrophy.