Objective:To study influence of type 2 diabetes mellitus (T2DM) on ambulatory blood pressure (ABP) levels and blood pressure variability (BPV) in aged patients with essential hypertension (EH) .Methods:A total of 80 aged EH +T2DM patients treated in our hospital from Jun 2014 to Jan 2016 were selected as observation group ,another 80 aged pure EH patients were selected as EH control group .The 24hABP indexes and BPV indexes were compared between two groups . Results:Compared with EH control group , there were significant rise in 24h mean systolic blood pressure [24hSBP , (126.47 ± 9.64) mmHg vs .(134.98 ± 10.63) mmHg] ,nighttime mean SBP [nSBP ,(125.73 ± 10.19) mmHg vs .(133.74 ± 11.29) mmHg] ,daytime mean SBP [dSBP ,(128.29 ± 10.97) mmHg vs .(136.42 ± 12.18) mmHg] ,daytime mean pulse pressure [dPP ,(59.46 ± 10.79) mmHg vs .(65.38 ± 11.69) mmHg] ,nPP [ (58.00 ± 10.11) mmHg vs .(67.14 ± 9.93) mmHg] and 24hPP [ (59.27 ± 10.16) mmHg vs .(64.76 ± 11.62) mmHg] , P<0.01 all;and significant rise in 24hSBP standard deviation [24hSBPSD ,(12.63 ± 2.87) mmHg vs .(18.41 ± 3.09) mmHg] and nSBPSD [ (10.14 ± 3.53) mmHg vs .(14.89 ± 3.54) mmHg] in observation group , P<0.01 both .Conclusion:Diabetes mellitus elevates daytime and nighttime SBP ,increases BPV and risk of cardiovascular diseases in aged EH patients .