Suddenly stand up black eyes, dizziness, mostly due to the role of the earth’s gravity, the lower limbs blood or other parts of the body of the blood is not easy to return to the body, the emergence of postural hypotension caused. When there is a black eye and dizziness, if the conditions can lie down, or take a sitting position, raise the legs can be relieved. If you sit for a long time, the blood in the lower limbs is not easy to return due to the earth’s gravity. Therefore, when suddenly stand up, the role of gravity highlights the role of the earth, lower extremity blood or other parts of the body blood, obviously showing a downward trend. If the basal blood pressure is not too high, postural hypotension is especially likely to occur. The first person who cannot tolerate such low blood pressure is the brain, and thus dizziness occurs. Because the fundic artery is also a branch of the cerebral artery, when the blood supply to the brain is insufficient, the fundic artery must have insufficient blood supply, i.e., there is a transient blackout, which can be considered a physiological phenomenon. Especially when squatting and standing up, most people will experience transient dizziness and blackness in front of their eyes. Special attention should be paid to the fact that if blackness occurs when sitting still, it is basically a pathologic factor, and the cause of the disease needs to be clarified in a timely manner by consulting a doctor.