Abstract: Objective To study the basis of Aloe extract in treating hypertension in animal experiments. Methods Hypertensive rats were given NG-Nitro-L-arginine (L-NNA) for 4 weeks to produce hypertensive model.Fifty hypertension rats were randomly divided into five groups:model group,the high,middle,low dosage group of the Aloe extract[300,150,75 mg/(kg·d)]and Enalapril Maleate tablets group[20 mg/(kg·d)],with 10 rats in each group.additional 10 rats were chosen as control group.Given rats corresponding intragastric administration daily,while the the control group and model group with distilled water.Non-invasive blood pressure measurement was used to detect SAP,DAP,MAP and heart rate once a week for 4 weeks.After four weeks of treatment,blood was collected from the rat abdominal aorta for determination of serum nitric oxide NO and superoxide dismutase SOD activity and level of Endothelin.At the same time,heart tissue was embedded in 10% neutral buffered formaldehyde fixation,paraffin and sectioned,and then to observe the histopathological changes after HE staining. Results After four weeks of treatment,the high,middle and low dosage group of the Aloe extract and Enalapril Maleate tablets group significantly lowered the SAP (t=4.648,P<0.01),DAP (t=6.469,P<0.01),MAP (t=8.731,P<0.01) and heart rate of rats compared to the model group (t=4.390,P<0.01).Meanwhile,the Aloe extract and Enalapril Maleate tablets can significantly increase NO (t=6.183,P<0.01) and SOD (t=8.502,P<0.01) content,markedly decrease the content of ET (t=5.719,P<0.01),but they have no significant difference.The treatment groups decreased heart thickening and kidney weighting,and could moderate damage of heart and kidney. Conclusion Aloe extract could reduce blood pressure in L-NNA induced hypertensive rats,and the results suggested that the antihypertensive mechanism may reduce blood pressure by improving NO availability and decreasing the content of ET.