Brain hemorrhage caused by a car accident is often severe, and the danger period is usually about 2 weeks. After a car accident patient develops a brain hemorrhage, he usually goes through three periods of rebleeding, cerebral edema, and related complications. Re-bleeding occurs within 72 hours of the initial brain hemorrhage; cerebral edema peaks 3-5 days after the injury and begins to subside in about 1 week; and related complications occur within 2 weeks. Therefore, the dangerous period of cerebral hemorrhage in car accidents usually takes about 2 weeks to pass and at least 3 weeks to be fully stabilized. In a few patients, the condition may recur during the recovery period and may enter the dangerous state again, such as lung infection in the later stage, which may lead to respiratory dysfunction. After a brain hemorrhage caused by a car accident, a timely visit to the emergency department requires close attention to changes in the condition, and early surgery or conservative treatment can be taken to stabilize the patient’s condition.