Aim To investigate the correlation between blood pressure variability and heart rate variability in patients with hypertension and diabetes. Methods 90 cases of essential hypertension were selected as hypertension group, 92 cases of hypertension combined with diabetes mellitus were selected as hypertension combined with diabetes group, 90 cases of healthy people were selected as control group at the same time. Glycated hemoglobin (HbA1c), serum creatinine (Cr) and fasting plasma glucose (FBG) were determined. 24 h dynamic electrocardiogram (ECG) and ambulatory blood pressure (BP) were synchronously measured, and each index was calculated automatically by computer. The differences of general condition, heart rate variability and blood pressure variability in the three groups were compared, and the correlation between the indexes was analyzed by Pearson. Results The differences of HbA1c and FBG in the three groups were statistically significant, there was no significant difference in gender, age, blood lipid and Cr. The indexes of heart rate variability of hypertension group and hypertension combined with diabetes group were lower than those of the control group (P＜0.05), and the indexes of heart rate variability of hypertension combined with diabetes group were lower than those of the hypertension group (P＜0.05). The differences of SBP, DBP, SSD, dSSD, nSSD, sCV and dCV in the three groups were statistically significant (P＜0.05), which were higher in the hypertension group and the hypertension combined with diabetes group than those in the control group (P＜0.05), and which were higher in the hypertension combined with diabetes group than those in the hypertension group (P＜0.05), and the differences of DSD, dDSD and nDSD had no significance in the three groups (P＞0.05). There was a negative correlation between 24 h mean systolic blood pressure standard deviation SSD and SDNN, SDANN, rMSSD, SDNNIndex and PNN50 in hypertension group and hypertension combined with diabetes group. Conclusions Compared with hypertensive patients, the impairment of autonomic nervous function in patients with hypertension combined with diabetes group is more obvious. The blood pressure variability and heart rate variability of follow-up patients are helpful to assess the condition and improve the prognosis.