Abstract: Acutely increased intracranial pressure （ICP）and sequential alteration in vital sign, pupils and electroencephalogram （EEG） were observed in cats treated by inflation of the extradural balloon. The baseline intracranial pressure （ICP） was 2-12 mmHg. When it rises to 38.89+2.0 mmHg, declining amplitude and frequency of EEG appeared; to 41.1±1.95 mmHg, the respiratory rate decreased; to 49.5±2.64 mmHg, the ipsilateral pupil enlarged; to 66.19±2.56 mmHg, both pupils dilated; to 71.22±3.21 mmHg, the blood pressure elevated; to 78.50±5.69 mmHg, the EEG curve became flat; and to 83.25±5.49 mmHg, the apnea occurred. In the discussion, author put forward some points for paying attention in making experimental model of increased ICP, analyse the connection between alteration of ICP and Cushing’s response and agree to take ICP＞40 mmHG as a severe intracranial hypertention.