Informed consent right was one of the patient＇s legal rights in the medical activities. Based on the multiple role and special statue of hospital side in the medical activities, it should be given to freedom corresponding to the right of defenses under certain conditions. In general, the following would be formed the defense causes of medical infringement on informed consent right of the patient: enforced medical behavior of the doctor side, the discretionary behavior of the patient side which be informed obligation by the doctor, the failure of the obligation because of irresistible force or accidents, the informed consent right which was refused and abandoned by patient and having faults when the family members acted as the agents, etc.