6-year-old child with a fever of 40 ℃ can be seen in influenza, intracranial infections and other diseases, whether there is a danger need to be based on the etiology of the comprehensive judgment, such as serious intracranial infections may be dangerous, such as the emergence of brain hernia life-threatening. 1. Influenza: for 6-year-old children in the course of the disease can appear body temperature of 40 ℃, often accompanied by dizziness, muscle pain and fatigue and other symptoms of general malaise, more than a history of epidemiological exposure, generally mild cases of children with active intervention (such as reasonable fever, under the guidance of a doctor to use oseltamivir phosphate, etc.) without significant risk, the prognosis is good. However, it is necessary to closely monitor the mental status of the child during the course of the disease, and observe the recurrence of temperature. If super-high fever occurs, or the temperature does not go down after treatment, serious complications may occur, and there is a danger. 2. Intracranial infection: it can be caused by bacterial or viral infection, and clinical symptoms such as high fever, convulsions and depression may appear. If the condition progresses rapidly without timely intervention and treatment, it may be dangerous, such as causing cranial hernia with cranial hypertension, which may jeopardize the children’s lives. 3. Other: such as acute leukemia, is a common malignant tumor in pediatrics, may appear the above symptoms, accompanied by skin and mucous membrane bleeding, etc., bone marrow aspiration examination can assist in the diagnosis, the diagnosis is clear because of the high degree of malignancy of the disease, that there is a risk of the disease, need to be actively intervened in the treatment. If a 6-year-old child has a fever of 40°C, it can be seen in a variety of diseases, and should be actively consulted by a specialist physician to assess the child’s condition and determine whether it is dangerous.