To investigate the effects of impaired glucose metabolism (IGM) on cardiovascular autonomic nervous systems in essential hypertensive (EH) patients by comparing heart rate variability (HRV) and blood pressure variability (BPV) in EH patients with or without type 2 diabetes mellitus (T2DM). Simultaneous 24-h recordings of ambulatory ECG and blood pressure monitoring were performed in 36 male old patients with simple EH and 33 male old patients with EH combined with T2DM. HRV analysis included time domain parameters such as SDNN, SDANN, SDNNi, rMSSD and pNN50, and total spectral power (TP) of HRV, which mainly consists of VLF, LF and HF component along with LF/HF ratio, was also obtained. The value of ambulatory blood pressure was represented as the mean blood pressure (mean systolic/mSBP, diastolic/mDBP and pulse pressure/mPP)during different periods (24 h/24 h, day time/d and night time/n). Standard deviation (SD) as well as coefficient of variance (CV) of blood pressure during each above-mentioned period were obtained to reflect the long-term BPV. Our result showed that SDNN, SDNNi, SDANN, rMSSD, PNN50, TP and HF of HRV in cases of EH with T2DM were all significantly lower than those in simple EH subjects (P＜0.05). No significant differences in VLF or LF was found between the two groups (P＞0.05), while LF/HF ratio was significantly higher in EH with T2DM patients than in simple EH subjects (P＜0.01).Moreover, dmSBP, 24 h-mPP and dmPP were all significantly higher in EH with T2DM patients than in simple EH subjects (P＜0.05), while nmSBP, 24 h-mSBP, 24 h-mDBP, dmDBP, nmDBP or nmPP showed no significant difference between this two groups of patients (P＞0.05). And dSBPSD,dSBPCV and 24 h-SBPSD were all significantly higher in EH with T2DM patients than in simple EH subjects (P＜0.05), while the other BPV indexes showed no significant difference between this two groups (P＞0.05). It is concluded that the cardiovascular autonomic nervous systems in EH patients was further impaired by T2DM, displaying lowering of HRV and enlargement of BPV, which in turn induced abnormal structural and functional changes of cardiovascular systems. Therefore, improving cardiovascular autonomic nervous systems might reduce the occurrence of cardiovascular complications in the EH patients with IGM.