The difference in blood pressure between the right and left arm is <10~20mmHg is normal, too much difference may exist on one side of the arterial lesion or aortic coarctation. Since the heart is located on the left side of the chest cavity, the left subclavian artery originates directly from the aortic arch, and the right subclavian artery originates from the trunk of the head and arm, the blood pressure of the right arm is generally higher than that of the left arm, and the difference can be as high as 5~10mmHg. The difference between left and right arm blood pressure should not exceed 10-20 mmHg, within this range is mostly physiologic, and exceeding this range generally suggests the presence of obstructive lesions, stenosis, or aortic coarctation and other vascular diseases in the subclavian or brachial arteries on one side. It is recommended that people with large differences in blood pressure between the right and left arms should consult a doctor in time and undergo CT angiography of the aorta and ultrasound of the upper limbs if necessary.