Objective To study the relation between elderly hypertensive patients with accompanying type 2 diabetes mellitus and characteristics of ambulatory blood pressure. Methods 46 elderly hypertinsive patients with accompanying type 2 diabetes mellitus (experimental group) and 46 patients with essential hypertension (control group) through 24 hours use MEIGAOYI ambulatory blood pressure monitor. Results Comparison finds elderly hypertinsive patients with accompanying type 2 diabetes mellitus have lost normal blood pressure day and night rhythm, especially in aspect of obvious increasing of systolic pressure load and night systolic pressure. The results showed statistically significance (P<0.01,P<0.05). Conclusion For such elderly hypertinsive patients with accompanying type 2 diabetes mellitus treatment on high blood pressure should not only lower down too high blood pressure, but also lower down blood pressure steadily throughout 24 hours in the day and resume day & night rhythm.