High blood pressure of 260mmHg is very serious and carries the risk of cerebral hemorrhage, hypertensive encephalopathy, and acute heart failure. High blood pressure of 260mmHg is a serious elevation, which will cause serious pressure on the blood vessels in the body such as the heart, and the following dangers can occur. 1. Cerebral hemorrhage: Cerebral blood vessels will be subjected to greater pressure when blood pressure is elevated, and the presence of atherosclerosis or cerebral aneurysm in the patient can lead to sudden rupture of cerebral blood vessels, resulting in cerebral hemorrhage, which is life-threatening in severe cases. 2. Hypertensive encephalopathy: The sudden rise in blood pressure can also lead to hypertensive encephalopathy, in which the patient can suffer from severe headache, nausea, vomiting, and in severe cases, even consciousness disorder, which is life-threatening. 3. Acute heart failure: Elevated blood pressure can significantly increase the afterload of the heart, resulting in increased work done by the heart, which may induce acute left heart failure if the blood pressure level is elevated for a long period of time. The risk of significantly elevated blood pressure is very high. It is important to visit a hospital in a timely manner to quickly lower the blood pressure level under the guidance of a physician to reduce the risk caused by elevated blood pressure.