The present invention discloses a manufacturing method of an over-current protection device, characterized in that the PTC plaque is conducted by punching under frozen state to form the over-current protection devices so as to reduce the heating and temperature rising in the PTC plaque due to punching and temperature difference between the metal foil and the conductive composite material. Relatively, the deformation and stress of the over-current protection device caused by punching will also be reduced. Therefore, there is no need for additional process to increase the temperature sensitivity and electrical property stability of the over-current protection device.