Blood pressure comes down after deep breathing mainly because the vagus nerve is excited when you breathe deeply. Deep breathing can regulate the pressure in the chest cavity and increase the circulating blood volume to the heart, as well as relieve stress and soothe the mood. These can promote the excitation of the vagus nerve, causing the release of acetylcholine, which has a negative effect on the heart, thus reducing the heart rate, diastolic peripheral vasculature, increasing the volume of blood vessels, reducing the pressure of blood on the walls of the blood vessels, so that blood pressure falls. Deep breathing has a certain effect on the decrease of blood pressure, but it cannot replace the effect of antihypertensive drugs. When the blood pressure is lowered by deep breathing, if the blood pressure drop is not satisfactory, oral antihypertensive drugs should be taken in time to lower the blood pressure. Long-term elevation of blood pressure will lead to a series of adverse consequences, so life should be active long-term control of blood pressure. It is recommended that patients with high blood pressure go to the hospital in a timely manner, under the guidance of the doctor to carry out standardized treatment, do not self-diagnosis and treatment, in order to avoid delaying the condition.