Before invasive therapy, the patients have the right of informed consent and the doctors are under the obligation to inform. However, due to the effect of the medical paternalism and commercialization, some doctors are used to making decisions for the patients. Therefore, the intention of the relevant civil law will fail. In fact, doctors who are in a monopoly position in the medical knowledge and technology are considered as a power to restrict. So informed consent should be a constitutional right, and it is necessary to understand this right from the perspective of constitutional law.